There are quite a few "canvas-only" environments now (like Create.js that they built it for)... my favourite in Ejecta http://impactjs.com/ejecta - that let's you wrap up your canvas games/experiments in an iOS app that run really fast (for canvas!)... the guy re-implemented most of the canvas API on top of openGL.

I used to get a good frame rate even on my ancient iPhone 3G. I used simple old-school style bitmap fonts there, though. More retro ;)