depends on what kinds of games you like... if you like realistic games, then nfs and team fortress won't do u any good.
if you're looking for the most popular online games, then a quick look at xfire will show that cod4, cod2, css, and a few others are on top (wow is an exception, cause it's gay
)
but personally, i like GTR: Evo (realistic racing game), cod4, and some other games to pass the time til mw2 comes out...