I came to this forum accidentally while looking for a bittorrent search aggregator (finding bit che), and registered for this thread, and will probably never post in this forum again.
I love all of the games (the ones I've played, at least) that have been mentioned - I'm more into RTS games than FPSs, but I have to say that, without a doubt, the best game ever created, by far, is a game that came out about 2 years ago, I never thought anything of it, and picked it up one day in a bargain bin at K-mart for $15, thinking it wouldn't be that great, but it turned out to be the most amazing gaming experience I've ever had. That game is "brutal legend".
It has SO MUCH of all of the elements that I love about my favorite games, plus an AWESOME soundtrack (esp. if you like heavy metal), incredible world detail, the art, the cut scenes, everything... it's just a near perfect gaming experience.
The game play itself has sent SO MUCH serotonin coursing through my brain that I'm still amazed I can take pleasure in anything else.
It has the best of RTS and the best of action-oriented games. You can interact with every type of character in the game using double-teams, and everything - from the music, to the fighting style, to the characters, to the world - which is just a work of art - is all based around classic heavy metal, which performances and cameos by Rock Legends.
It is, without a doubt, the single greatest game ever made, and for some reason, it seams as if nobody has every played it.
Before this, my two favorite games were GTA4 and AOE. This game blows them both away.
Oh, and the most deliciously evil game playing experience ever is to play as Emperor Deviculous.
Here is a clip showing the first 5 minutes of gameplay in story mode:
http://www.youtube.com/watch?v=ys0VbktA-0I