My problem w/ a lot of MP games is this: the MP is often meaningless to me.
Here's why. When you play many MP games, you are often doing what is a "skirmish" mode. You basically are playing against other players and bots. Then, you're done. Next time you come back, you feel like you're starting all over again. There's no feeling of any continuation nor is there a feeling of much of a purpose.
What is lacking? Often, it's a campaign. This is where I think MMO's like Guild Wars succeed -- they give the multiplayer gamers more than just skirmishes. Guild Wars gives you a campaign and storyline to go through, like when you do a campaign in a single player game experience. Doing a campaign w/ other fellows gamers can be a great, fun thing. That's what I love about Guild Wars -- I feel like I have the best of SP world, which would be a campaign; and the best of the MP world, which would be playing with other gamers.
This is where I think The Crossing might succeed online where many MP's have often failed me -- the fact it's based around some sort of storyline and campaign might give me plenty of reason to play. It's just a matter of this -- will The Crossing implement this well or not??? I think Arkane's on the right track. Though, given Arkane's track record w/ bugs and performance issues, I think The Crossing will probably succeed, after a few patches are actually implemented.
Don't get me wrong. I like MP, but it just often feels to redundant and routine. CTF, DM, blah blah blah. Only so much of that I can take.