Multiplayer games taught me that I generally dislike other people.

Sorry in advance to people who hate talking about it but Dark Souls is a very paradoxical experience It can:

• Help you learn patience and awareness
• Help you learn not to stress over losses
• Help you learn that people have different experiences of enjoyment and understand your scope of interest in games.

Bethesda games taught me to save at every opportunity

I’m surprised not to see more people mention From Software games. Going all the way back to demon’s souls they consistently teach you how to understand the tools at your disposal, the challenge that you currently face, and how to use the former to overcome the latter. I learned how to “read” opponents to find and exploit vulnerabilities while playing dark souls way back, and that general approach is consistently useful in all sorts of other games. There are lots of other translatable skills involved, of course, like timing and resource management.

getting incredibly good at Quake back in the day made me good at basically any first person shooter game that you put in front of me

Rocket League. If I can reach my fast moving targets without having to adjust pitch, roll, yaw, and thrust, all at once, from a third-person view, there's just no challenge.

Counter Strike: raw aim, how to outsmart opponents, perfect practice makes perfect and if you put enough hours into anything and do it correctly/good, then you can get good at almost anything.

Path of Exile: Taught me about being efficient. If you're repeating the same action 10,000 times, if you can cut even 1 second off each time you do that action, it adds up over time to a significant amount. And then you can try and cut another 2 seconds off...then another second.

Celeste was the first "hard" game I played that I actually ended up 100%ing. It's so fun and makes me try harder on other games too

This is admittedly kind of an oddball interpretation of "better gamer", but my personal take on that is being able to enjoy games more, as opposed to any measure of skill in playing them (and also understanding that there's a lot of overlap there, but humor me for a sec :P).

Perspective: currently in my mid 30s, peak gaming for my childhood was competitive shit like the N64's Smash Bros (which is the best Smash Bros. Fite meh.) or 007; fast forward to some racing type games, COD... the thing those all have in common was that the fun was in defeating your opponent, and any aspect of the game that wasn't competitive just kinda automatically felt not fun. Nor was getting stuck in a losing streak from playing against people better than me; or winning streak from playing against people who weren't challenging to beat. The window of potential to actually have 'fun' was shockingly narrow.

The game that kinda pulled me out of that was Halo CE. Right out the gate, it looked like any other shooter, and it had a rapidly growing community and the competitive elements that caught my initial attention. Fire it up, and it IMMEDIATELY stood out as something special. Up to that point, videogame music was pretty much exclusively simple digital sounding jingles, so the Halo CE login screen music hit like a fucking truck. I start up the campaign, and experience another first: the story had me hooked. Campaigns in shooters only ever felt like a tutorial you have to sit through to not be terrible in multiplayer, but Halo CE was like a full-blown movie, with each scene supported by a literal symphony.

It made me look at games differently - things like Zelda had flown under my radar, cuz what's the point if there's no multiplayer?? Not even score to compare?? Got myself a copy of OOC, and "...oh, that's why."

So, long story short, Halo CE was my gateway drug into RPGs.

More in tune with OP's question though, it kinda yanked off the blinders that stopped me from fully enjoying parts of some games, or entire genres of games.

...and that whole spiel is ofc relative to my subjective experience to the gaming industry circa ...idk, 1995+? So, Halo CE probably won't hit the same against today's gaming industry: but keep an eye out for games that blend elements you know you enjoy with material you haven't really dabbled into - you could unlock an entire new genre of awesome experiences.

Crusader Kings reminded me that losing can be fun

Sekiro

Many games come down to finding some unbreakable combo of buttons or abilities and when you have that figured out you steamroll the game. To successfully finish Sekiro, you must be patient. Learn when to let your enemy attack, so that they leave themselves open or provide you with a chance to parry.

There's no leveling up to get so strong you can thrash any boss, like in other souls games. You just have to learn the game mechanics and get good.

Quake 3 Arena and Unreal Tournament. In my opinion, these are still two of the greatest games of all time. You don’t get better because your character or weapon is better. You get better because you put in the practice. you improve your reflexes. You learn the arena. Every player starts every match on an even playing field. Every frag feels like an accomplishment.

I appreciate that modern shooters are trying to do something different with every iteration. But stuff like call of duty, overwatch, or destiny never captures that magic. In many ways, they felt more like slot machines.

Halo got close, but I always felt it was too slow. And also, I felt Tribes was the better series for online play that felt similar. 

Hollow Knight 100%. Its also my favorite game.

Dark Souls, don't give up skeleton, rethink your strategy and learn what's being thrown at you, you'll get through it.

Eve Online taught me that math + leadership are effective ways to win. Also the importance of thinking strategically and weighing risks.

World of Warcraft taught me that many people are willing to craft items all day, if it earns more in-game gold than actually doing anything fun in the game (actually in hindsight this was true of Eve, and real life for that matter). I sort of... ran an exploitative in-game sweatshop producing things for the in-game markets (e.g. not involving real money or anything that violated the rules of the game).

These two groups of realizations made me pretty good at online games for a little while! My gaming hobby came to an abrupt end when I realized I could just... start a company IRL and be paid non-virtual money.

Not that it’s much of a benefit today as RTS games are barely nonexistent. But StarCraft 2 taught me all about macro management. Spending them resources and building an economy.

Portal was my first FPS on a computer. Got me to practice using mouse and keyboard and now I can't imagine playing an FPS with a controller

When I was a kid it took me 2-3 weeks to beat the Flight School mission series in GTA: San Andreas, and although I hated nearly every minute of it I did become a better video game flier.

Gta vice city as I learned how to type properly as I couldn't figure out how to pause the game to type aspirin with 1 finger. Does that count?

Hades. I used to hate hard games. Hades taught me to get good.

Six-ish years ago I would say Overwatch. It was my first online multiplayer FPS and it fosters a lot of skills. Teamwork, communication, mechanical ability, game sense, ability management, managing tilt, etc.

Too bad Blizzard decided to stop new content for Overwatch 1 for years, only to reintroduce Overwatch 1.5 with an upgraded battlepass and cash shop monetization scheme. I don't get how people are still playing after what they did to it.

WoW increased my typing speed and accuracy as without voip, its essential to communicate effectively.

World of Warcraft. 12 years of playing and raid/guild leadership helped me learn how to play, not just play. How to:

• Theorycraft
• Research how to improve
• Maximize output and/or efficiency
• Take advantage of class synergies in games
• Understand the importance of area of effect, burst damage, sustained single-target damage, etc.
• Understand damage mitigation vs avoidance, and where each is valuable
• Play to my/my team's strengths, rather than simply doing what is "best"
• Better recognize trends in game mechanics to anticipate what may come
• Recognize the valuable portions of a game's user interface and maximize its visibility while avoiding clutter

I had learned portions of these things in other games, but my leadership role in WoW pushed me to truly understand many things that aren't a major focus in most games.

I have two answers.

First, my general reflexes, situational awareness in games etc. were strongly improved thanks to Doom Eternal. The game keeps you stressed and engaged the whole time (especially on the harder difficulties) and you have to be very quick. It was the first time I needed custom keybindings to be fast enough to solve some sections. Switching between 8 weapons, sometimes after single shots, is something you have to get used to, but it's incredibly fun!

Second, specifically for 6DoF navigation, Outer Wilds was incredible. When I started I could barely make the spaceship go anywhere without exploding, now I feel I could be pretty good at a 6DoF racing game!

This dates me somewhat, but trials maps in UT2004 helped me develop a lot of precision and fast fingers.

It was a multiplayer FPS, but it had cool mobility like double-tap dodges, double jumps, wallkicks, and crouch jumps. And they could be combined in many ways, so there were platforming levels of varying levels of difficulty. Diagonal dodge-doublejump with a wallkick at the very end to get onto a platform that's like 4 inches square, type of thing.

No one gonna say it?? No one?

Fine.

Cuphead

The 3 that stand out the most for me thinking back on it

Typer Shark and Mud's (typing skills)

Really helped me get down my typing skills which translates to a lot of pc based games (even just chat). Mud's were some of my favorite fast paced games (multi-user dungeons). Godwar's was my shtick and as a Drow character you had a lot of powers you had to get out before an opponent could notice and respond to your presence.

MechWarrior: Sega Genesis (team work skills)

This was a crazy one I would play with family. There was a co-op mode that allowed one person to control the bottom half while the other person controlled the top half of your mech. You really had to cooperate and work together so it didn't turn into an actual physical brawl because of the frustrations.

Call of Duty: Zombies (game mechanics)

This was probably my first game that I really got into game/enemy mechanics. To survive to higher rounds you had to adapt and know what the zombies were gonna do. Later iterations kinda destroyed that feature with zombies stumbling and etc but I get they were trying to stay innovative and fresh, still killed the genre for me though.

Honorable mentions are the great RTS's that were everywhere in the 90's. Starcraft for sure but even blizzards previous Warcraft's and then of course C&C and even Dune (another sega game but solid RTS for it's time). Really though the skills for RTS's don't translate as direct to other games anymore (just got me better at the RTS's that I love) as more and more they become hero focused like what they did with WC3.

edit: grammar

StarCraft 2

Mostly for building in-game awareness. Helped in a lot of games, even FPSs. Just always being proactive when facing some kind of meta.

The Lord of the Rings: The Return of the King (PS2).

You either learned, or you quitted.

I Wanna Be The Guy: The Movie: The Game

If you know, you know.

Rhythm Games in general, but specifically osu!mania taught me that I can, like, actually get good at completely new stuff no matter how much I suck at it to begin with

It also taught me that I really like Hardcore EDM, before hand I wouldn't really listen to music cuz I wasn't sure exactly what kind of music I was drawn to

Elden Ring.

I didn’t love the learning/difficulty curve of Soulsborne games until this one, but it got its hooks in me hard.

I usually spammed most boss fights and played everything a certain way, but here I had to learn the boss’s moves and dodge, parry and use power ups to bring them down.

Worth it. While frustrating, it made me return to other genres and play them again but differently. Hitman, sniper elite, roguelites/likes, anything that rewards patience, really. These now had a whole new facet I didn’t see before, or I did and I was applying it to these games.

I’ve since tried other soulsborne games, and while I now appreciate the difficulty and find them a lot more fun, the exploration and world of Elden Ring was the difference maker for me. It was being able to forge my own path and choose my challenges.

Red Dead Redemption 2 taught me once again to slow down and take all the time I want with these huge games. I've saved a ton of money since.

In relation to skill, playing a ton of the original Halo on Xbox at my friend's house while being only a PlayStation owner got me really good at using arbitrary controls.

GTFO. It has honed a ton of skills for me. Coordination/cooperation, accuracy, ammo conversation, fast problem solving, the ability to switch from fast to slow and back very quickly, the list goes on. It's the most intense game of red light green light I've played.

Megaman X - Probably the best Action Platformer ever, it teaches you all the basics of the genre through gameplay alone.

Metal Slug 2 - Cuphead too hard for you? Then give this good ol' classic a shot! It has simple yet fun mechanics and you can go as trigger happy as you want. And don't feel bad if you play on Free Play Mode, what matters is that you have fun!

Gran Turismo (PSP) - If you want to get into the series (or into Racing Simulators in general) this is probably your best bet, you have all stages available from the beginning and very little customization, but you can feel the progressiveness of the game as you buy more powerful cars and unlock higher difficulties.

Grand Theft Auto III - This game can be really hard at times (no swimming, only 3 safehouses, cars are really fragile, etc.) But once you understand the mechanics of the game and you start getting better, the rest of the series is a piece of cake. (Also, i loved the freedom you had when performing most missions in this game, it makes sense that later titles restricted you due to being more "story oriented", but GTA V's missions really just feel like going through film setpieces that is boring :/)

Unironically old school runescape. Playing it for years ingrained the concept of efficiency into me. Now I'm able to do well in games where mechanically I'm still shit because I'm constantly trying to use my time as efficiently as possible.