Gears of War 1 and 2 - God knows how much time... Probably with the two games combined I would say around 1000 hours, possibly more. It is not uncommon for me to play the game for 5 hours in a single day sometimes. The definitive "go to game" for me these days...
Oblivion - around 100 hours
Pokemon Gameboy/GBA/DS games - probably around 300 hours combined. I believe Pokemon Red alone burned about 100 hours. Me and my friends were REALLY into that game back in the day.
Everquest - around 200 hours maybe? Though this is also a very rough estimate. When through a huge Everquest phase with a few friends, where we played almost every day during the course of a couple of years, sometimes over 4 hours a day.
Everquest 2 - 100 hours approx.. Didn't get as into this one as EQ1, as my friends who were playing the game with me all decided to bail for WoW, leaving me in the dust.
Mario Brothers 3 - Probably around 100 hours as well. One of my favorite games to this day. I played it so much as a child even my parents eventually got into it, and they rarely play video games.
Super Smash Bros/ melee/Brawl - Between the 3 Smash Bros, probably a good 200 hours. Nearly a hundred hours of Brawl, mainly playing online w/ my cousin.
Starcraft - Probably 100 hours. One of the few PC games I play, yet one of my favorite games. I still occassionally pick it up and start playing again, never seems to get old.
