Official Mario games haven't been 2D sprite sidescrollers in a loong time but everyone here only ever makes those. Even worse, people seem to only ever make the same kind of sidescroller and try to copy the original physics and feel. It's old and boring.
Then there's the lack of interesting 2D sprite content. A goomba will always only be able to walk unless someone puts in the effort to sprite new animations. If you're a lone programmer, you're probably not going to. So your game will just have vanilla enemies doing what they usually do. If you're a spriter, then you probably don't have the programming skills to actually do anything. If you're a spriter and you're not developing a game, it's unlikely your going to just make sets of new animations since you don't have a concrete use. As a result, we see the same over used graphics over and over.
I'm not asking for people to make original games, just not .. out of date games.