Which game?
Currently there is Counter-Strike. It's attempting to be something else with the much delayed release of Condition Zero sometime next year.
Competition is currently standing as Rainbow Six 3: Raven Shield. Rainbow Six being the de-facto counter-terrorist game. But then, around there same time, but the same makers we have Splinter Cell. Which is currently released on the X-box and is making everybody go "oh my, wow, that's lush" etc.
Raven Shield multiplayer demo is out, and is great fun. The question is, which one will win? CZ? It's CS, which everybody likes, but they have removed all the likeable things and turned it into a R6 spin-off, with dated graphics.
RS? It currently has the PC market excited. But then there is SC, which is also getting attention. So which will win? I'm going for Splinter Cell, because it's released a month earlier so the dedicated servers will go for that. Justification for hosting both is tough.
Why not CZ? Well, lets face it. It's old and ugly.