Hmm, that's odd. Granted, there's rather a big difference between Portal 1 & 2, but I loved the second one as well. I didn't burn through it repeatedly like I did with the first, but I did complete it during the first week I had it.

Furthermore, when I later played through the co-op campaign with a co-worker (not on company time, mind you), a whole new dimension to the gameplay opened up. It is without comparison the most fun co-op experience I have ever had in a video game.

The Might and Magic RPG series and, yeah, Ground Control series. I consider GC 1 better than the second. So i recommend at least one playthrough. GC2 was got out before DOW and it's less clunky than the DOW series. Also, a hell of a lot more tactical.

I join the Portal 1-2 group. Especially Portal 2 :D

But it's nothing comapred to RPGs. As an RPG-maniac, I can think of 2 games that hooked me in an (almost) unhealthy way.
I recently finished Baldur's Gate 2 for the first time, and I was literally playing it for a week every day from 10am to... 1am. I only stopped to take care of my basic needs...
The other one was the first 150-200 hours of Skyrim. I sometimes forgot to eat, because I was playing all day long ._.

Now that I think about it, I could say the same about almost every RPG I've played... I think I'm seriously addicted to RPGs ._.

From non-RPGs I can think of Dishonored. I could't stop playing that game.

Another game that really hooked me was Hostile Waters: Antaeus Rising. It helped that it was extremely surprising as well. I had never heard of it before it came to GOG, so I didn't expect too much. What I found was a game that catered to my tastes to such a degree, you'd think it had been developed just for me.

That's funny. I had the exact opposite experience with FreeLancer. It was supposed to be this truly open-world experience, but what happened to me was that the game quite soon drew me into a completely linear series of battles, with no opportunity for effecting repairs inbetween them. I think I finally died during the 8th consecutive battle with no end in sight, and uninstalled the game in disgust.

Nice, thanks for mentioning this! I always like a good space game. Also, I guess I'll have to play the Portals now, then.

Oooh I will do this as a long, one-breath list of my "all time favs" ... ready?

Tie FIghter, XCOM, Civ, Privateer, Diablo, Baldur's Gate, Half Life, System Shock 2, Mass Effect, Fallout 3 / NV, Dark Souls

and maybe Dark Forces belongs in there, but more for the setting and OH SHIT I CAN LASER STORMTROOPERS!?!?!?!

Contra
Tecmo Bowl

Sacrifice. In fact, I think it's the only game I've played recently that actually held my attention :P

I'm still at that stage with Master of Orion as well. As far as MoM goes, the right-click help system really helped a lot. After getting familiar with the game, the wiki helped me with advanced play.

the game that hooked me right now is shadow run returns ^_- most read only storys end up boring me to death
this one though i find to be humor and good

I'd say Demon's Souls for PS3. What hooked me was the monster and environment design. always pushing to see what the next hideous creature would look like or the next environment would look like. The music helped to.

The difficulty didn't really matter to me, made it all the much sweeter when I arrived. The place that made it all worth while was the prison... the memories...

Recently, Wasteland 2. I'm just loving the game, just wished I had more time to play.
Civilization 4 I am still playing to this day.
Baldur's Gate Series

Oh wow I've been eagerly awaiting Wasteland for a long time now... is there an open beta I don't know about? Or is a backer beta / test phase? If so any word on when they're going to release (I've been keeping my fingers crossed every month since Sept / Oct). Thanks!