Eh. A good multiplayer element can help a game's shelf life considerably. A lot of games with both elements tend to suffer in one aspect or the other.
I myself tend to look more towards single player aspects of games because I'm just not that much of a social player. With multiplayer games, I like to play with my friends, and that's about it. I've more or less ignored the online aspect of games like Dawn Of War 2, Burnout: Paradise and Halo just because I despise dealing with Random Internet Assholes.
At the same time, I do wish some games, like say, Torchlight for example, did have multiplayer support because friends can always make mere fun into true enjoyment.