As reported yesterday, the new TMNT: Smash Up for the Wii seems to borrow liberally from Super Smash Bros. We're not going to argue about the "fairness" of lifting from other games to make your design, because appropriating other people's ideas and resynthesizing them is basically the essence of art. And every fighting game since Street Fighter II has cribbed from Capcom's masterpiece anyway. Basically, we wouldn't have a fighting genre if not for copying.
But on to Smash Bros. and the Turtles. Do you think the Smash Bros. gameplay is strong enough to work without Nintendo characters? Are there any particular ideas involved in the bizarre fighting series that more fighting games could stand to inherit? And is it going to become its own branch of the fighting game genre?