With HTML5 and CSS3 you can do anything you can do in Flash without all that bugginess and mismemory management. For instance you have Canvas where you can do any kind of drawing. With CSS animations you can make it look like anything.
Mark,
I interpreted Rogerio's question exactly opposite to you. I think he is asking if you can use HTML 5/CSS 3 instead of Flash. To which the answer is definitely yes.
There are some pretty cool HTML 5 games already which show the capabilities of HTML 5. I'm sure there will be more after more HTML 5 is supported.