Speaking of beat-em-up replayability, how come they never made a game in the genre which is like Diablo with random dungeons?
For example, you are in a factory stage, why not make it so the stage and boss and weapon layouts are random? Perhaps have rare items pop up from time to time and you do all of this online co-op. I imagine if all the assets are in the game, there has to be a way for this to happen.
Maybe you break open a barrel in the fire stage, and 1 in 1,000 chance the ice stage boss happens to pop out. Perhaps you are online and your group happens to wander into another player controlled team on the same stage? Just an idea, but people play the same stages in Halo and COD over and over, why not in this genre? Just unlock special moves or by building exp.