What is your favorite game?

Terraria

As of right now either CS:GO or GTAV or Trackmania.

Forever and ever:
"Master of Magic"
Linky

and welcome to the site. nice of you to join the discussions so fast (i was a lurker for like a year ;) ).
hope you read the FAQ and you will enjoy your stay here.

I have played CS:S so often and long it would be wrong not to mention it here. :P
I'd have to say Memoria though (together with the first game Chains of Satinav).
I probably should also mention Neverwinter Nights (1) since I played that a lot.

my old favorite game was Colonization (1994). now i would say it's Starcraft 2. it just never gets old, and i can't wait for the new expansion.

Enemy Territory. I've Enjoyed playing this multiplayer game. I was on a Team, we did some competition.
At first, I was playing 6 hours straight everyday... I was SO addicted to it. When I say addicted, I mean it... But it was really fun, and frankly I still consider it the best Multiplayer FPS of all time same as Quake III (This is my personal Opinion). Sadly this game is dead and lost contact with all the friends from the lovely community of http://www.crossfire.nu/

Duke Nukem 3D is my number 1 game over and over and over again. :)