Diablo 2 (including Lord of Destruction) for almost two years.
Morrowind for almost a year.
Currently somewhat addicted to City of Heroes.
Snood
Dr. Mario
Tetris
Bookworm
Hexic
Zuma
Acno’s Energizer
Insaniquarium
Gold Miner
The Sims
Those YetiSports penguin-tossing games
Quite a lot of those are from the addicting games website. A VERY DANGEROUS site if you tend to get hooked on games. Each of these games captivated me for a certain length of time, during which I would stay on the computer till 2am saying “just till I get to the next level” or “as soon as I get to 56000 points…”
I refuse to let myself get into those online RPG things. Oh, I know I’d love them. I’d be great at them. But I’m still in school and should probably sleep from time to time.
My addiction was Ultima Online. I would spend hours playing it every day. When I wasn’t playing it, I would spend a lot of time thinking about new character templates, money making schemes, house decor, etc. But, after a year and a half, I began to grow bored with the game and finally cancelled my account.
I’m happy to say that I’ve been UO free for over two months now. 
My name is viva, and I have a serious problem with AOL’s Pogo games.
First it was Word Whomp. Then along came Sweet Tooth, soon followed by World Class Solitaire, then Tri-Peaks solitaire, then Perfect Pair Solitaire.
Right now I am addicted to Mahjong Garden. It’s so bad that when I go to bed, I see visions of little tiles dancing in my head.
Damn games.
Metroid Prime, Pokémon Blue and Gold (hey, it’s a pretty darn good RPG. I’m not ashamed!), Goldeneye, Perfect Dark, Tetris, Chip’s Challenge, Sid Meyer’s Alpha Centauri, Super Mario Sunshine, Metroid Zero Mission, all the Zelda games except the gameboy ones, GTA 3 and Vice City.
Emulation has introduced me to whole new 8- and 16-bit worlds of addicting games: Super Metroid, Super Mario Bros. 1 and 3, Final Fantasy 1 (I have this opened up in FCE Ultra in a background window as I type this!), Chrono Trigger, Final Fantasy 3, Master Blaster, Secret of Mana.
Marry me!
Snood and SimEarth. I had to uninstall them from my PC to keep from playing them. Of course, I’d reinstall them sometime later and play and play, and the uninstall them, and then reinstall them and play and play.
I’ve been SimEarth free for about eight years now, and Snood free for two years.
You only want me for my game library, I know it. But marriage is not out of the question if we can have duplicate game consoles. I am not necessarily against playing on a console while someone else plays on a computer. There’s nothing quite like finally getting up from a serious gaming session, scarfing down fast food, and discussing the game with someone who also CARES about the game.
One thing about Secret of Mana…level up your weapons and magic skills at the Ice Crystal Forest (I forget exactly what it’s called) each time you get a new Mana Seed.
At the moment (and for the forseeable future) it’s Natural Selection. I’ll get on a good server and suddenly three hours have passed. Yeesh.
hehheh, okay, I’ll bite.
Hello, my name is Ellis, and I’m a game addict.
[entire crowd]: “Hi, Ellis!”
[woman in second row]: “We love you.”
[old man cackling from back row]: “It works if you work it.”
I had to uninstall and physically destroy my copy of Starcraft. Before that, Age of Empires claimed oceans of my time.
On a less-hardcore scale, I ran up $30 in late fees (on a buddy’s account!) from Blockbuster when I couldn’t come up for air with Hitman 2.
Currently, I deal with my need to play Hitman: Contracts and EA’s Fight Night on a one-day-at-a-time basis.
This post is, of course, all in good fun, and not meant to belittle any 12-steppers out there. But really, some 12-steppers take themselves a little too seriously.
In high school, Civilizations II. My mom would announce that dinner was ready, and I’d say “Just a minute!” The rest of the family would eat while I continued to conquer the world, and maybe an hour or two later I’d finally eat my cold plate of food in the kitchen alone.
In college, I had two: The Sims (already mentioned by many) and Princess Maker 2. The latter is a Japanese child-raising sim that was supposed to be released in the US about a decade back, but the English-language version never made it past the beta stage. I got a copy off the Internet one fine Saturday and played it for six hours straight. Then I went to the dining hall to get some dinner. Then I played it for another three hours. Realizing that the game was essentially digital crack I refused to tell me friends where I downloaded it from, but they eventually found it on their own. The addiction spread like a virus throughout my social circle…although I must say with some pride that I was the only one who ever managed the ultimate “Ruling Queen, married to the Prince” ending without using the cheat code. 
2D spaceships flying around shooting bullets on each other and bumping into walls. Who would have thunk that was a winning concept. 8 years of online play. Forced to quit due to lag, otherwise I’d have kept going. Logged around 3000 hours of playtime, which is small-time compared to some other people.
Hell, now I’ve done it. Lag looks fine for the time-being, and I’ve got the week off.
DAMMIT!
I have played Toejam and Earl obsessively in the past. I just obtained another Sega Genesis system and I LOVE to pop in that game and play for hours upon hours. I’ve only ever won using a Game Genie, as there is no save on it and it just takes like 10 hours to come even close to winning. It remains the best game win sequence EVAH, IMHO.
I used to be obsessed with Q-bert when I was a young 'un. Imagine my delight to discover my local ice cream store has a Q-bert machine. Rock on!
Oh, and I do SO loves me some Sims! Can’t wait for Sims 2!
Yet another Civilization 3 addict checking in.
I also have been, am now, and will forever be addicted to the Forgotten Realms computer RPGs, especially Gold Box games (back in the day) and Baldur’s Gate I and II.
And yet another Civ addict checking in. Civ, Civ II, Civ Gold and now Civ III.
I bought Civilization (the first) on a Friday evening on my way home from work. I installed it and played continuously for the entire weekend, with only two six hour breaks for sleep, and about 10pm Sunday night, I started telling myself “OK, it’s time to put this away and get some sleep so I can get to work in the morning.”
Six hours later, I finally go to bed only because I can’t keep my eyes open, and my alarm is going to go off in three hours. So I wind up calling in sick that Monday…
… and playing Civ all day long.
The only other game that has compared to that was Gemstone III, the predecessor to Evercrack. I’m suprised I haven’t seen any other references to it on this thread. I was addicted to Gemstone on AOL back during the hourly rate days, racking up $400/month AOL bills.
Man, do I miss those days… <sigh>
Football Fanatic. A text-based soccer management game. Nothing too special, but I just cannot stop myself. Still trying to bring Chelsea FC from a divison D team to an A team in under four years. (Worth a download if your into those sports management games.)
SuperMario 3, Tetris
Warcraft II
Dungeon Siege
Dungeon Siege (Legends of Aranna)
Any version of Mahjong
Hoyle Board Games version of Scrabble
At home I’ve been addicted to Vice City for the better part of the year, I’m just not sure what more there is to do, now I just kill policemen and hookers for fun.
At work though, I waste gobs of time (on break and lunch only, of course) playing the freely downloaded Jardinains
I never could get into Civilization.
However, I’m in Gemstone, which is now GSIV. I usually play at least an hour a night. I USED to play six or eight hours a day, but I’ve had to quit doing that because I really can’t sit for that long. I’m a 53 level dwarven warrior (female), Master of Voln, Warrior Guild Master (master of tackle and warcries), and feared throughout the lands because of my feather collection, which I use to tickle helpless folks.
Simu restructured GS, because the game got unbalanced at high levels. The highest attainable player level is now 100.
Everquest for four years. Just recently beat my addiction. Before that it was Unreal Tournament. Now I just started to get back into Neverwinter Nights again.