Super Smash Bros Brawl. I most likely have played it for over 600 hours. I can't think of any other game where I've spent that many hours on it.

You can always use one of these

It will give a nice contrast with your avy's grey dress.

Lol, thanks! Though people would probably look at me weird around here x D

Actually, the dress is a sweater, but people can't really see it from just the avi pic ^.^;

Pokemon Diamond is my largest save with like 700 hours

I have over 2,000 hours in TF2 on Steam.

Keep in mind though i've been playing it for like 3-4 years though. 

civilization 1 & crusader kings 2, both over 2000 hours !

Everquest 1 played 7 years too.

Bloodborne over 500h

I'm at 600 now for Rocket League.

Between 2005 & 2012, I was really into multiplayer gaming, in competitive play

- Probably 4000h of EVE online. Stopped because I prefered my personality in game than my real me irl, which is a really weird situation ^^ .... stopped because gfs ^^
- Roughly 800h of UT2k4
- 500h for TF2


Now I'm playing a lot of solo games, my recent highlights would be

- MH3 Wii : 250 hours in two month (started my day waking up early, before work, by planting, chasing herbs and bugs for potions, then making runs for Lagiacruses at night, ahh good times.)
- I should have around 500 hours of The Witcher saga (TWI + II + III, and the adventure game which is supercool)

- Obviously SSBM : 700h, around the same number for MKDD (that's what you get when you try to beat the 150cc all star mirror cup in co op with several friends), FZero GX a couple of hundreds of hours....

Age of Empires 2 would be my most played game, but it doesn't track time so I'll guess around 1000+ hrs