I think when the original Final Fantasy came out on the NES, I could classify my playing as an addiction. No game has captured my attention like that.

Lineage 2
Resident Evil (Original/Director's Cut)
Final Fantasy VII
Star Ocean: The Second Story

Diablo
Diablo 2
Neverwinter Nights persistent world play
Lord of the Rings Online

Fallout 1
Jet Set Radio: Future
Counter-Strike 1.6
Half-Life
but the biggest one I've been addicted to was Zombies Ate my Neighbors. I litterally sat down and played 'till level 35 died, then got back to 35 without a cheat because I always forgot to write them down.

I believe I have been addicted to a few Video Games.

Most Notably:

Skies of Arcadia: Legends
Valkyria Chronicles
Bioshock (for the story mainly and the atmosphere).

Those ones were my main addictions.

Diablo 2
Starcraft
World of Warcraft
Doom 2

Not addicted to anything at this moment, though I am playing Diablo 2 again, just casually this time. Looking forward to getting my fix with Diablo 3 though.

Addicted to WoW for a month. Then got bored.

I have a WoW addiction(they say the first step is admitting you have a problem)

im currently playing Atlantica Online and i say i am addicted to it...

but not as addicted as me playing Final Fantasy games before (not the online version) and other RPGs i could get my hands into...

I'm pretty certain I had a clinical addiction to Runescape for nearly two years, back in highschool. I eventually climbed myself out of that rut, though.

'course, now that I have four months off, I seem to be descending into a Fallout 3 addiction. Yee, and haw!

I really say these weekones need to be closed after the week is over.

Yeah I've had a few addictions over the years. I played World of Warcraft for four years (I started not long after the beta) and played far, far too much for at least one and a half of those years. I was also temporarily addicted to Mass Effect due to its awesome storyline.