Is HTML 5 worth your time? http://oreil.ly/bkBf0m – HTML5+CSS+Javascript = yes but Flash has headstart on development environments.
HTML5 itself and Flash are vastly different. They have different things that they’re trying to do. But the HTML5 plus CSS plus JavaScript package is more. I think that’s an easier comparison to make to Flash because Flash is supposed to be this total environment. You can put things on the screen and you can script it and you can define interaction. And HTML5-CSS-JavaScript lets you do that as well.
We got to the point a couple of years ago where the HTML-CSS-JavaScript stack can technically do just about anything that the Flash environment makes possible. It’s just a lot harder at the moment to do that in HTML5-CSS-JavaScript because Flash has about a decade’s head start on authoring environments.