Btw, is it only PC games you're after as there are some damn addictive console/handheld games too. I thought I'd give Patapon 2 a quick 5 minutes and an hour later I've had to put it down.
If you liked WoW at all, you might want to consider a "WoW Emulator Server". I haven't played any but I have heard great things about them. Last week I started playing on an old Everquest emulator server and it's absolutely amazing, but the old graphics turn some people off. I got used to it really fast though and now I love playing it. I can't stop... System Shock 2 is pretty easy to get working. I have that working on both my XP PC and my Vista HTPC and it plays great. I even have it working with modern, full, wide-screen resolutions. Fantastic game. The first system shock though.... ouch! I tried desperately to get that working and I actually managed! (after a LOT of hard work). But I forgot that it was one of those FPS's from a time before the mouse look revolution. IE: The mouse only rotated your character left and right, to look up and down, you had to use PG UP and PG DN. I couldn't find a way to make the mouse let you look up and down like modern FPS's. So I could play it but it was frustrating for me because I'm so used to be able to freely look anywhere now, so I just gave up. I will stick to SS2.
Sniper Elite Total War series Richard Burns Rally (with logitech MOMO wheel and few tweaks... AWESOME)
Heroin! Oh wait. Thats not a game.... hmmm.... If you are looking for a free game or mod I would recommend looking at Dystopia or Insurgency for Steam. (HL2 mods)
If you've got a 360 available I've been totally hooked on PGR4 for a number of days now... Oh the noise!
If you love the Diablo series you will probably love Titan Quest (and the addon Immortal Throne). IMHO it's actually better than Diablo, with really lush graphics and great game play. I'm usually a diehard CS fanatic, but right now I just cannot put TQ down. Apart from that there have been a number of great suggestions; first and foremost give System Shock (2) a go. It probably doesn't get much better than that, although the graphics are a bit dated.
Has anyone mentioned EVE Online? And if you'd rather not pay to play, (although you can play it for free after a few months) the X2-3 games?
I take personal offense when I see EVE recommended now. I held it in quite high esteem, and always assumed it was pretty good, until I tried the trial. It's basically the WoW/Everquest/FFXI mould with no graphics, decent voice actors, environments or sophisticated social process aids to soften the grind. As with all MMOs, the rewards are to be reaped about 50 hours into the game - but you'll spend all that time up to it, and all your time afterwards, staring at a black screen with a small, badly animated ship in the middle of it and some bits of text floating around. Honestly, it's such a cheap, lo-fi game I find the pay-to-play requirement genuinely insulting. There's more creative force behind games like Darwinia than there's ever been behind EVE Online. [/rant]
Can I politely ask the last time yourself played the game? True there is a little grinding to do, as with all games you need to get established in it, and I'm not just talking about MMOs. Every game you play, the more you play the better weapons you have access to, or better units or more money or better tech etc etc. IN EVE the grinding factor is very different way from that of WOW - you don't have to be online all the time to develop your character - some aspects continue developing (ie skills) while your offline. EVE I believe is different form WOW and a number of other MMO, basically because of its community. The majority of players are generally of a more mature level and this makes the interaction between people a lot more fun and enjoyable. Also, in the last 6 months or so (I've only played the game in that for two months) there have been a LOT of changes to the graphics and the visual effects and the scenery. Even before it looked good, but right now it looks even better. It's some of the best virtual space you'll ever see out there and rivals that of X2/3. THe benefit of EVE is the game is continually being updated and improved and has recieved a number of updates to the graphics. The latest major patch/expansion has introduced more visual effects and tech 3 ships which look gorgeous. EVE online does have a steep learning curve, but the scope and sheer variety of things a person can do is what attracts me to the game. You can do anything you like in the game, and by joining a corporation and making friends it's a very fun way to pursue a career or several (like me) and have FUN! Besides after 3-4 months of playing (I'm just 2 so far) you can get yourself to a stage where your established in the game well enough to actually start paying for the GTC by in-game isk. This is perfectly legit - people who want a quick injection of in-game money buy extra GTCs and then convert it into an in-game object which they can sell. Other players give them the in-game money they ask for and the player who put it up for sale gets some quick cash. The Publishers still get their money though. If you haven't played it in a while try the game again - you can use as many free 14 day accounts as you like to try the game out!
pokemon on a gbc emulator, i'm hooked on crystal (oh wait, that didn't sound right), i mean pokemon crystal. and maybe try gta4, that got me addictd for a few weeks, but it is kinda short compared to the other games you guys are suggesting.