Everquest.

I had just under 300 days played on my main character, and that doesn't even count my alts.

I wasted waaaay too much of my life playing that game, lol.

PSO - Best video game experience.
Maple Story - 90 hours straight one time. fell asleep at the keyboard a few times.

Oblivion on PC.

Thats nothing, I probably have 800-900 days on all my characters combined in FFXI. Although a lot of that was AFK (probably 40% or so), so theres no way to really tell.

Pokemon and World of warcraft. Just stop playing WoW 6 months ago since I was having serious addiction and need to set time aside to pursue my other hobbies.

Counter-Strike.

 Wow Gobias...Thats a really, really, really long time...

I suddenly dont feel so bad about my addictions...

Diablo 2 without a doubt. Hundreds if not THOUSANDS of hours played.

Scratch that.  My own game. :P  Hours: 11662 That's just my admin. :)  My other characters have about 3k hours between them. :)

Indeed it is, I know people who have exceeded 2000 days (over 5 years) of actual playtime.

I don't regret any of it though, I love that game to death.

Probably Diablo2, with Guild Wars not to far behind.