Umm... No order...
Super Mario All-Stars

X-Wing Vs. TIE Fighter
Tetris
Jedi Knight: Dark Forces II (although I actually prefer it before using Force powers becomes essential)
Then it gets tricky; going by time spent playing, it might have to be Half Life -- I once played that game for about 48 hours straight!
I'm not a big gamer, and the most recent platform I had is a PS1 I bought cheap a few months ago, but when I get into a game I play it intensively at the expense of pretty much everything else until I've ODed!