Super Mario Sunshine (GC)

You know, I guess Mario kinda dominated my life.
Diablo II (PC)

The first time I ever considered myself addicted to a videogame was when I couldn't stop playing D2. I even went as far as purchasing a Stone of Annihilation from an online vendor for my Necro. Jeez, I had no life in Freshman year of High School thanks to this game.
Resident Evil 4 (GC)

I've spent at least 100 hours playing this game, which is shocking since that involves nothing but playing the single-person campaign over and over. (With a healthy dose of the Mercenaries on the side) Brilliant game, it's such a shame RE5 sucked.
Gauntlet Legends and Gauntlet: Dark Legacy (N64/GC)

Co-op play at its finest. For me, this stands out as the best cooperative videogame ever. Don't steal my ****ing treasure chests or I wont save you from the grim reaper next time.