Spider-man 1 made 821 million dollars world wide; Spider-man 2 only made 780 million. If SM2 was so good and helped out the third film why did it make less than it's predecessor and the next movie? It helped out the next film, but couldn't match up with the other two? That doesn't make sense. It garnered immense critical acclaim, but I'm sorry, that doesn't really mean anything if it can't match the hype of the movie that came before it. Which, obviously, it didn't. Numbers don't lie.
Batman Begins made decent numbers; the Dark Knight made over a billion dollars and is widely regarded as the greatest superhero film of all time. Of course that was going to carry over into the third film. So you can't really compare the two franchises here; Batman's gross continually went up and Spider-mans took a dip in the middle, which is the film that you think garnered all the hype for the third movie. Once again, doesn't make sense.
I vividly remember 2007 and the months leading up to SM3. The marketing was extensive, you couldn't go a day without hearing about it. And the hype didn't have anything to do with the second film, it was due to the trailers and marketing surrounding the movie. People were stoked to see the black suit and all the villains.