Team Fortress 2
Cruelty Squad (okay, the game is only a couple years old, but the art style is so intentionally shit that I just can’t see it aging at all)
Jet Set Radio, Jet Set Radio Future, and (I predict) Bomb Rush Cyberfunk. BRC also is only a couple years old, but it shares the same style as JSR(F), which has aged very well.
Minecraft
Doom and Doom II (just remember to turn off texture filtering, or set it to nearest neighbor).
The Sims. No, really, I think The Sims games have all aged very, very well. Some better than others, but I feel like each one of them has a visual style that still works today.
TF2 might be the best example of this honestly. It looks like it could have come out today.
Other than that god awful old-school Valve UI used for most of the menus/things.
