While I DO enjoy some online multiplayer in short quantities (The exception being Halo), I think that the outright focus on online multiplayer has skewed focus away from what's important. That being having fun. It's all about competition, leaderboards, K/D ratios, and all that nonsense. And EVERY GAME has to have it! BioShock 2's multiplayer was inexcusably shoehorned in, and not even up to the snuff of the less than average singleplayer. Assassin's Creed is even getting multiplayer, but I'll let them pass because they're being original.
What we need to do is just back off of the multiplayer for a year or so. Just... no MP games for a year. Then we'll have to work on the singleplayer aspects and making the game fun enough to play a lot on its own merits, THEN we can go back to making shitty multiplayer games like Call of Duty and I'll just buy all the games that come out that year and be happy.
EDIT: Yeah, and XBL is the asshole of gaming. I NEVER play with anyone I don't know in real life. I just can't bear to, what with its community track record.