I can agree,

It's just the fact that the demo is such a small portion of the game. Only five characters and one stage. And only two of those characters are newcomers. If there were, like, ten characters and five stages, then I don't think it'd be as bad.

The demo does exactly what it's meant to do, give you a feel for how the game feels and nothing more.
They want you to beg for more, the sick bastards. Great for generating hype for the full one though.