I've never experienced Crysis Wars, but I don't know that I'd directly compare MW2 to BF2. BF2 has that whole larger scale thing with vehicles and such, where MW2 is just traditional on foot gameplay modes.
Also, I just checked the other day and apparently 2 of the expansion packs are free now. I have just the base game, and the 1.5 patch includes 2 of the addons.