so as you see, zmatt, valve has released games that I am not to crazy about, but it really boils down to CS1.6, TF2, and L4d that I really like. L4d because its immensely fun to play with friends and compete against other teams. TF2 is pretty self explanatory, but I'll explain if I HAVE to. CS is a granddaddy of competitive FPS gaming. Everything about is amazing, now 1.5 is my favorite, but let's not get into that.
So just the way Q3 is still the best FPS and SC is still the best RTS, I like the majority of valve games because I see qualities that keep bringing me back to them.
Yeah l4d 360 version was the 7th highest selling title of 08 I believe, too bad the graphics too a big hit and they had to deal with little sticks.