Im not a huge gamer like everyone helse here are. But 217 hours on planetside 2, 102 on the new SimCity and 45 on Civ 5
I've put in a combined total of 160 hours playing Shenmue 1 and Shenmue 2 for Dreamcast.
I know it's a console game, but that game series was really good and from what I hear Shenmue 3 will be exclusive to PS3. If that is true then that is the only console I will be buying just for that one game! lol
Other than that the longest time spent playing a PC game will have to be World of Warcraft, I've been playing that game since beta in 2004.
However I recently dropped wow because I can't stand that they put freakin stupid panda's in it... I picked up Neverwinter and I am having a blast. I have about 120 hours into that and I like it so far.
i think I've invested over 1000 hours into the story and exploration of fallout 3, with mods and such.
1,728 (72 days and some hours.minutes etc.) Call of Duty 4
i have put 400 hours in Skyrim. there are some chests in my house i can not open with out crashing.
i put a bunch of time in minecraft
most of all i played Halo: Reach for 2 years forging maps for me and my brothers. i have done 2 runs of SLASO (solo legendary with all skulls on) there was a lot of dieing and restarts with that. do bad i do not have an exact number on how much i actually played. it was all offline :(