by Naomi Kokubo
I highly recommend Flash if your project includes online games. Yes, Flash doesn’t work on the iPhone and iPad, but you’ll probably want to do a native iPhone app anyhow. On the Web, Flash still rules, and when combined with Flex, it’s quite powerful.
The other comments talk about using HTML 5 if you’re not making games, but be careful if you’re doing this. You still need to account for the fact that Internet Explorer (unfortunately) still has about 60% of the web browser market share since it ships with all Windows boxes (source: http://www.engadget.com/2010/05/03/internet-exp…). If you’re not doing games, then by all means you should rock HTML5 but do it in such a way that it degrades gracefully using flash for IE and older browsers.