Games are still hard to do properly in the browser. Eventually, they might add OpenGL support to javascript, as well as full audio control. But I don't think that'll be happening for a while yet, so any app which does heavy 3D work or audio work will need to be native.
I don't see that happening any time soon. But whats true is that, not all games need to be 3D or fast paced to be fun. As a kid at heart still; I'm working on a few web based games with UI's for mobiles.
How about Google's recent O3D work? Not saying it's the be-all and end-all of browser 3D, but people are working on it.