I spent the weekend playing through Lego Star Wars 2 on co-op, and it was everything the original was and more. Everything that was great about the first was still intact, and they even added more items to collect and some cool new features. It also seemed like the game was more "lego-ish" than the last. They really made use of the two franchises. I'm definitely looking forward to that Lego Batman game they're working on, as long as it's got co-op.
I've said this a hundred times over, but not enough developers consider co-op play a viable game mode, and that sucks. But next month we've got Marvel Ultimate Alliance shipping, which, with online 4-person co-op, I'm really anticipating.
Also, Castle Crashers is at the top of my list, but isn't expected to hit the XBL Arcade until early next year.
In other news, shirts! Because showing nipples in public makes people uncomfortable.