Probably uncharted 3 multiplayer 400+ hour.

It's awesome and depressing at the same time. Wouldn't take it back though since I had so many great moments on it. 

Who knows how much I played Pokemon White and SoulSilver. Each say 999 hours but I'm sure I've already played twice those times, at least on White (I lost SoukSilver D:)

I know, it's a pretty nice record! I really like Quake III!

WoW- 10000 hours
LoL- 1200 hours
FFX-300 hours
Dynasty Warriors 3- 500 hours
Digimon world- 200 hours
Age of Mythology- 700 hours
Rome Total War, Medieval Total war, Stronghold Crusader, Civ 3, Civ 4. All 200 hours+

The Last of Us is my highest tracked game at 300 hours multiplayer and 50 hours of single player. Uncharted 2 is very close at somewhere between 250-300 hours for multiplayer alone.

There are a lot of games with much higher play times such as Football Manager, PES, Age of Empires, Pirates of the Caribbean, Diablo 2, GTAs, lots of RPGs etc. Who knows the exact amount, but there are many games with 500+ play times.

1500h+ on phantasy star universe

1500~2500h on Starcraft/Broodwar. It's impossible to give an exact count... What I know is that's about the only game I played for 3 years, played if for 3 months most of the days and nights of summer holidays, spent lots of week-end on it. that's the period I played games (in fact game) the most, and I even went back to the game a few times. Just for LAN time with friends I'm above 200 hours. Add to this more than 100 hours in internet cafe...

I had to quit the game, really, just like a drug, so I could pass my university exam.

Distributed over eight years, and over countless vacations:

Mario Kart: Double Dash!!

If my math serves me correct, I clocked more than 2000 hours into this game.

Others:
1000+ hours: Civ V, Plants vs Zombies, SimCity 4
100+ hours: Fire Emblem: Awakening, Bravely Default