I think I would enjoy the Mass Effect 3 multiplayer mode if the player advancement system wasn't basically the equivalent of playing with Pokemon cards.
Luck of draw determines what perks, weapons and even characters (each with unique loadouts) I get to use? Ugh.
Factor that in with controls and combat mechanics that never quite hit the level of polish in a Gears of War, and I'm pretty much done with it now that I've shipped off my dude to the front-lines.
It's too bad, because mixing up powers to deal with some of the more powerful enemy types is pretty fun (though it's only actually necessary on Hardcore difficulty or above, and against the Reapers... the Geth and Cerberus are pushovers).
But I prefer working with teammates to take care of setting up fortifications to delay, distract, kill or assist us in killing the waves of different enemies, and putting those smooth, polished combat mechanics to work against different combinations of enemies and bosses.
Ah well, each to their own. Somewhere out there, there are actually people who prefer the Survival Spec Ops mode in CoD to BOTH. :P