This is a simple game. However, it's too simple.

It's multiplayer, but the fact that it's multiplayer isn't used for any kind of challenge. Perhaps one of the cubes can jump on the other one to reach a platform that otherwise can't be accessed by a simple jump? Maybe one of them is invincible to spikes, allowing the other to jump on him (again) to cross a large gap of spikes? Maybe there's a button that needs to held down to open a gate, and one of them needs to stay on it so the other can reach another button that activates the same gate so the first cube can cross?

IDK, I'm just spitballing ideas.