Super Meat Boy?

I think it was Cave Story that prompted the modern indie revival of this genre

Bit.Trip runner

If you like the soundtrack for The Messenger, check out these "24 bit" remixes where they combine the 8 bit and 16 bit songs

https://youtu.be/vw_MX3Alq28?si=attcora0WAv6dB7H

Broforce is not that hard, but it's so fun that it might be worth a play.

Plok for SNES

10/10 soundtrack on this quirky platformer

You'd like 20xx and 30xx if you liked the Megaman X style of games, fjeyre all chip tune and in a similar style to what you've played. Also, Megaman X (and Megaman Zero, the continuation of the X franchise) are fantastic.

Music wise, give Spark Mandrill's theme a listen from MegamanX and tell me it doesn't hit just right.

Ninja Gaiden.

If you allow technical nonplatformers in there (Hollow Knight? If you are into Metroidvanias, play Super Metroid, it has great music. Also, Axiom Verge.) I could go up and down my various game collections for a while.

But in spirit of the actual question, here's one that I don't think anyone else here will recommend: LOVE. Simple, short, lots of room for mastery. And I like the music.

If you are a fan of the classics, the SMW modding community is huge. We have a wide variety of difficulties, and most modern hacks have all custom music- in engine, playable on console, ofc, so it's all 16-bit.

Micro Mages? Essentially a modern nes-game, co-op for up to 4 players.

edit: while not really a platformer (but does include platforming sections, iirc) and soundtrack does slap hard with the chiptunes: Retro City Rampage

Have you played La-Mulana or the sequel?

It's full of insane puzzles and traps, but it's a great metroidvania with some great music. It's one of my all time favorites.

I'm a big fan of those games, and I really enjoyed HUNTDOWN. It's a shooting platformer, more Contra than anything on your list, but is good times and has top choons to listen to while you're playing.

It's been a while since I played it, but I think They Bleed Pixels might fit the bill on both counts.

Also I recently started The End is Nigh which is another Edmund McMillen game very similar to Super Meatboy. Seems good so far.

I haven't seen this mentioned yet, so I'll say it: The End is Nigh. Shit's hard as balls but very fair and rewarding to play, only go for it if you're a real glutton for punishment.

I think you need to play Pizza Tower

super meat boy

Electronic Super Joy and Geometry Dash come to mind.

I used to like the music in some of the Mega Man games.

Rainbow island and the New Zealand story used to be my favourites. But I hate platformers, so not sure how that goes. At least there's some progression of difficulty in RI.

well... Street Fighter 2010 has IMO a great soundtrack, and it's kinda hard. Qualitywise... it's controversial.

I recommend Cyber Shadow. It's published by Yatch Club Games as well.

It's more of an action platformer, but a little obscure NES game from my childhood that deserves a loy more of attention: Vice Project Doom

Not really a platformer, and not really chiptune, but Katana Zero is pretty fucking great in the gameplay, music and story department.

People already mentioned VVVVVV here, so I'll go with the classics angle: the Donkey Kong Country series has phenomenal music and super tight platforming. Difficulty is a bit on the low side compared to something like Celeste, but there's absolutely a mastery curve.

This includes Returns for Wii/3DS and Tropical Freeze for Wii U/Switch.

The Adams family game for the NES.

I never could get past the freezer section, but I never got to try much. It was my cousins' game and they lived in a different state.

Megamen X3, but X1 and X2 are nice as well. Old but gold.

Not a game suggestion but a music one: Master Boot Record. It should match your style I think.

Axiom verge is a really fun metroidvania and from what I remember it has a killer soundtrack, synthwave. N++ is another platformer I highly recommend, awesome music, easy to learn and hard to master

DuckTales or DuckTales 2 for the NES playable in the Disney afternoon collection. TBH most of the games there should be your jam based on Shovel Knights influence.

Hollow Knight based though, Guacemelee is good, not sure about its sequel. Axiomverge too. But they are metroid like games so Super Metroid and Metroid Fusion would be another recommendation.