I still haven't seen any game made in flash of such epic proportions as Promqueen, which I and five others have been developing for a year, targeting the offline market. Since we were doing mostly turnbased game mechanics and made good use of flash's animation-friendly "stuff", flash came to good use. The game is however also stuffed into a wrapper to give it functionality beyond what flash can provide today.
So hell yeah. But it really depends on the kind of game your doing.

What I really appreciate flash for is it's user-friendliness and it's easy start for beginners. No other language, that I know of (but I don't know many), would give you the ability to make "your first game" in such a short period of learning.