You can play the game, no problem, with the base game alone. The other stuff is just extra content (a lot of it not terribly worthwhile, imho)
EDIT: what exactly do you mean by "play the game"? If you mean "play online with/against other players" or "play the campaign", then the base game is perfectly adequate.
I meant both. In COH1 You could just buy a DLC, and then play the regular game, and the DLC (the DLC contained the regular game too).
Thanks guys! I'll buy the game, and if I really like it I'll buy the DLC's.