Super Mario 64. It's fun and it still holds up.. mostly. I am trying to get all 120 stars but some are proving rather difficult. I really enjoy the amount of depth in the jumping and platforming mechanics, but the camera is just plain bad by today's standards.
As for any current video games, I occasionally run around Guild Wars 2, and the new Unreal Tournament is pretty fun for a round or two. I want to give Deus Ex 3 another go because I haven't touched it since release and I rushed through it back then.
I'm really just waiting on games that haven't actually come out yet, like Playtonic's own game