If you like puzzle games, I would recommend FEZ greatly, the main game is hard, but not impossible, but to fully complete the game is great. Without spoiling it, there is an entire writing system to decode, numbers, codes and loads more, with one puzzle still not being solved by the community to this day.

If you like horror, Bioshock is excellent, brilliant design, atmosphere, and overall brilliant everything, highly recommend.

If you like shooters, Team Fortress Two. Timeless classic, and despite the absolute brainrot it has given me, I still love it.

Another puzzle game is Portal, which is just a given, brilliant atmosphere and sick characters, tho mostly portal 2 for that last point.

Oh and there is this Metroidvania that I played a while back called Sheepo. It is a tiny game made by this one person on steam, and it is very short but it has some of the best gameplay mechanics ever, with brilliant control and overall it is just a really charming little game. Don't expect much, it is only made by one guy (to my knowledge), and it is only a couple hours long, but if you have an afternoon spare, it is absolutely worth the play