First games I remember playing, at least on console, were Mario Kart 64 and Super Mario 64 on my cousins' Nintendo 64 (which later got passed down to me). I would frequently get Mario stuck in the castle moat and my cousins would have to get him out of it so I could keep playing, haha.
Pokémon Mystery Dungeon: Explorers of Sky
In terms of mainline games though, I'd probably have to go with Blue version, since it's the one I've spent the most time with over the years