(Saw this question asked on another popular link aggregation website and it got me thinking)
If you could play one game for the first time all over again, what would you choose? This might be because you want to do it all again, or because you don't think you got enough out of it the first time. It could be experiencing the game exactly as you were back then, or experiencing a game with what you know now.
For me, it's Legend of Zelda: A Link To The Past, experienced exactly as I was back in 1991.
Nothing comes close to how jaw-droppingly amazed I was by that opening sequence. The epic orchestral score, the cinematic rainstorm, creeping around in the dark... it was a generational leap above anything I'd played on 8-bit computers and consoles, and even the Megadrive. I'd love to play it again without thirty plus years of Nintendo/Zelda knowledge, or without knowing about the dark world.
If I were to experience it as I am today (and judge it versus games with modern graphics etc), I'd pick Ori and the Will of the Wisps. It quickly became one of my all-time favourite games, and I finished it three times in a year when I discovered it. Beautiful in so many ways.
Half-Life is probably the game that has had the biggest impact on me, though, so that would be my pick if I experienced it as I did around 1998.
You might like Black Mesa. It's a faithful remake of the first Half Life. It really nails the atmosphere and feel with modern graphics.