http://www.newgrounds.com/portal/view/308690
Super Mario Bros. Z is a series of animations that revolve around a deep storyline. It's best known for its intense action scenes. There are currently 8 episodes, each one ranging from 10 minutes (Episodes 1 and 2) to an hour (Episode 7). I do know that fan fiction/animations are often frowned upon, but trust me, this one is not like the others. I suggest to at least watch the first 2 episodes.
Keep in mind that the episodes are very far apart when it comes to release dates. It normally takes at least a year to make an episode, depending on the length. It's normally worth the wait, though.
I've been watching it since the first episode was released, like 6 years ago. Too bad he's slacking for a year before he makes a new episode.