This app was mentioned in 5 comments, with an average of 4.20 upvotes
Timberman has a similar type of gameplay. I am not sure, but timberman probably started this type of gameplay.
https://play.google.com/store/apps/details?id=com.dm.timber
Rush fight (not exactly 2D) implements the infinite stairs like gameplay too though it may not appear as such without playing.
I think you've got that the wrong way round, since timberman has 5mil-10mil downloads on Google Play and kung fu man has just 10k-50k (and it looks like not much more on iOS). Now it's possible that Kung Fu Man came first and got really unlucky but I doubt it. Does anyone know how to see the release date of apps on Google Play or the iOS App Store?
EDIT: Tweet from the developer confirms that Kungfu Man is a clone of Timberman, not the other way around.
It's freemium on mobile