Why does anyoen need to sell you on anything, just play the other three games (which you have obviously already played one) and decide whether you like the series. If it is a series you completely and wholly enjoy then get it, but if you only like the multiplayer then you may want to wait. The camaping of mass effect games has always seemed to be a far bigger part of the game than the multiplayer (typical with RPGs). But the choice is yours, to me the best way to decide on a sequel of a game would be to play the previous games.