1.Team Fortress 2/Super Mario World (I couldn't decide)
2.Bioshock
3.Left 4 Dead
4.Assassin's Creed 2
5.Glover/Super Mario 64
To be honest, I love the Mario Series since it's probably been the game that's always been there growing up (And even beyond), So I didn't think it would be too fair to just list them all 1-5... Plus i'd have a hard time choosing, as if it weren't hard enough.
But I absolutely adore TF2, play it constantly - and although it's pretty good on the Xbox it is MUCH^100 more better on the PC (More updates, no monthly fee, and the updates are not just minor technical fixes either.)
ro Street