What do you mean by "small definitions of better"? Can you do a cartoon with synchronized sound with HTML5? Better is a matter of "does it work for enough of your audience that it makes sense to build it".

If you know your audience and can push the technology, by all means go for it! GitHub has exactly that audience. They aren't idiots for going with canvas - for them it's a savvy move. But the Flash option is still there for a reason too.