How do endless runners fare?

I'm working on an "endless runner" type game for my first complete project, mainly because its compact and easy to manage. I'm not much of a game player myself, so I wouldn't think any endless runner would be that fun (this project is for learning), but of course some actually do well. So how do endless runner games usually fare? What would you do for different levels; or would you just stick with the one and make sure to implement GC?
Comments
This was my effort:
http://gamesalad.com/game/27640
It did enough differently to justify a purchase from some, but a lot gave it a miss I'm sure because they'd had their fill of runners, or because they didn't like the style maybe
QS
Dr. Sam Beckett never returned home...
Twitter: https://twitter.com/Quantum_Sheep
Web: https://quantumsheep.itch.io
@ QS
Have you ever considered remaking the game with all new artwork/theme? Just to see how it does? In my current project, we're debating whether or not to go Angry Birds style, or more graphic novel style, and I'm thinking, maybe introducing one of each. The gameplay would be the same, but the artistic stylings would be drastically different. I'm curious if you've ever done this, or seen it (succeed or fail).
It's certainly an idea, but not one I'd entertain, personally.
I've seen it succeed though. It's called 'Pokemon'
QS
Dr. Sam Beckett never returned home...
Twitter: https://twitter.com/Quantum_Sheep
Web: https://quantumsheep.itch.io