I think the Shank and Dishwasher games are the most satisfying modern beat em ups on XBLA. Button mashing won't get you far in those games, and it will take some skill to beat the hardest difficulty modes.

Scott Pilgrim is alright, but the graphics/sound is where most of the charm lies. Your character becomes totally overpowered about halfway in and the gameplay just gets stale fast. I had no desire to revisit it after my initial playthrough. I also think they really dropped the ball by not including online coop.

Best remaster of a classic beat em up is Final Fight by a mile.