Yeah it looks like Ruffalo's Hulk is going to be the break through character from this movie from everything I've read about it so far, which is kind of what I expected, he's also who I'm most excited to see (other than Cobie Smulder's Maria Hill). I still think we'll get a Hulk movie sequel for 2015. It's possible that the television series might interfere somehow with this but I doubt it.
I can certainly imagine this Hulk being very popular. Ruffalo's performance is excellent. He's a very gregarious actor - to me, at least - but he pulls off a really nice balance between warmth and threat, which suggests the Hulk lurking unseen.
And when the big guy does break out, Whedon does a brilliant job of combining ferocity with laughs. In my screening, the two biggest (i.e. loudest, longest) laughs of the film were down to the green dude.