I recently came across an interesting game called the "Everyone Has A Level" project.
In the game, there are 20 or so (very) short levels and each one has a different set of sprites for the player, the obstacles, and the tiles, these sprites are made by various people who volunteered to contribute to the game. Along with this, a lot of the levels give the player an extra ability such as double jumping, a gun, or a down-slam power. I found it oddly interesting that sometimes the extra ability had no purpose whatsoever in a level.
I would say that this game would be very much benefited by more levels and an addition of some unique gimmicks and obstacles. But for now, it's one of those games that lasts for 5 minutes and leaves you wanting more. It has a lot of potential, so I hope the creator (RoyTheShort) expands the game a bit!