Now, I don't not speak for a good portion of the CBM community, but this is why I think people get excited when a movie has box office success. People have been getting excited over box office success of Superhero films, since The Dark Knight broke records. I am pretty sure the people who were bragging about Dark Knights success then are the ones now complaining that everyone is excited over The Avengers box office success.
I see it this way when it comes to people bragging about box office. Yes we as fans do get something out of this. We get more quality films from the studio who created it. We know multiple sequels will be made that we enjoy. And hopefully more Comic book movies from all of the studios. We do not expect to get a cut, we expect to have more entertainment.
Put it this way and I hate using a sports analogy:
Why do sports fans cheer at games? They are not playing, and they are not winning, but they cheer and want there teams and players to do well. Why? Because they want to see them play more later in the season. The Avengers was like a big sports game It was like the game before the Super Bowl, we wanted it to be good so we could see it get more successful.
Phase II of Marvels plan is kind of like Our Super Bowl, it is a culmination of what we love from the Avengers. The Dark Knight was another very successful "team" and we beat it. It is all in good fun, it is nice to see a film you like being successful, especially when it knocks down ones we find crappy like Transformers 3. All in all we do it in good fun. Well I do anyhow.
So say you are a Red Sox fan, and you have been losing every season, bu a few seasons ago The Yankees won the World Series, and you are just wishing this year they would make it. Then it comes down to the big game between Red Sox and Yankee's and the Sox win. You get excited and throw a fit and say "WE are going to the world series" And you brag to friends who are not fans of your team. You rejoice, even though you as a person will never see any of the money that the team is getting, and will never get the same recognition.
This is why most fans (Well me anyway) Get excited over the Box Office success of Something. I hope this clears a few things up. :)