Isn't this space really crowded already, though? Especially if you consider flash games? Is your thinking that with HTML5 you can get onto platforms where flash won't work such as the iPhone?
I reckon if you could fashion a site quickly enough that would work on the iPhone and iPad, you would have a winner.
There's a large swathe of the population for whom http://www.pogo.com is the beginning and the end for games, and I would be the intersection between them and the iPad is going to get bigger and bigger.
