Over 300 hrs?
Hmmm......OK i know for a fact Star Ocean 3. My first playthrough was like 130+ hrs. My second playthrough was like 270+ hrs. After i realized how much time i spent playing that video game, i got a life. I barely pass 50 hrs on any video game anymore. Its usually 30-45. The last game i spent over 50 hrs on was FF13. I have 71 hrs right now and counting. I LOVE THAT GAME!!

EDIT:  I forgot Pokemon Diamond.  I spent like 320 hrs on that game.  Probably around 10 different playthroughs.

WoW

And the closest games to that are:
Team Fortress 2
and
Warcraft 2

Oblivion, Pokemon Red-Gold, Fallout 3. Diablo 2, MW2, Age of empires 1&2
Super smash Bros Melee

Warcraft 3: TFT/DOTA
But thats pretty much it.
300 hours is a lot of time to be spending on a single game, i dont think i've done it for anything else. I just reached 100 hours for Oblivion though

Oh yeah I definitely reached that on CoD 4 online.

WC3, Diablo 2, WoW and FFXI..

Wow, Blizzard you have stolen so much of my life from me :P

Monster Hunter Freedom Unite, Warcraft 3: The Frozen Throne and some MMORPGs I used to play.

I wish I was committed as you guys. I most I've ever gotten was 160+ hours on Uncharted 2 online.

According to Xfire (PC):

	Counter-Strike: Source	14 hours	690 hours
	Return to Castle Wolfenstein Multiplayer	< 1 hour	598 hours

Garry's mod is close, needs 31 more hours.
Age of Empires 2... Xfire didn't exist yet, but I know that more than 300 hours, easily.

More:
GTA San Andreas (PS2)
Goldeneye 007 (N64)
Mario Kart 64 (N64)
Super Mario 64 (N64)
Pokemon Red (GBC)
Pokemon Gold (GBC)
Super Mario World (SNES)
And probably Donkey Kong Country 3 (SNES).

All of these games are f***ing amazing, these are THE games.

And now that I think about it:
Runescape (Yeah I know)
Silkroad Online (YEAAAAAAHHHHHHHHHHHHHHHHHH)

Yeah...

...

Holy shit.

EDIT: Me when a kid + Nintendo consoles = A freaking beast

Me nowadays + PC Online games = DAAAAAAMN

But I'm glad to see I'm not alone...

Did you do all that with a guide? Because it's pretty much impossible to do everything and find everything in the game if you do not know where you're going and where to find all the things. 

And about the mods. OOO 1.3 alone can take you up to 100 hours to finish 100%, even if you use the walkthrough on Jorge Oscure page. Mainly because, unlike the vanilla game, enemies have fixed levels, and some of them are well over 50. Plus, you level up 4 times slower than in the normal game, which makes for massive durability.

And then, if you use FCOM+Warcray then you've got virtually unlimited durability.

Heck, even without using mods, the official expansions alone will take you more than 30 hours, and that's using a guide. Knights of the Nine is a 5-10 hours, while Shivering Islands can take you well over 20 hours to complete with everything.