All 3 of these films have the potential to be the biggest film of the summer (Hobbit notwithstanding), but what are the factors that benefit each film, and what detracts from them. I'll leave out the inherent quality of each film and internal advertising as they're pretty much universal for all films.
Avengers
Advantages:
Crossover appeal. Although each film has already established mini crossovers between each other in the previous films, this will be the first time they are on screen together, ala Freddy vs Jason. While most who have seen Thor/Cap/Hulk have also seen IM, some bleed over should occur.
Consistently solid films. Although I personally don't find the films to be as great as others (Singer's X-Men films are my Marvel standard), the general populace has been impressed with the films overall thus far and Iron Man has been a proven box office draw, so it should have good word of mouth to carry over.
3D. But primarily overseas. 3D may not help domestically but it is a big draw internationally.
Whedon. Though he's pretty much a god amongst comic geeks. Though his name will have about as much impact on the film's numbers as Kevin Smith's would. Still, every bit helps.
Drawbacks:
Popularity. As big as these characters are, they are simply no match individually for Bats/Spidey in the realms of pop culture, so unless the 3D and bleedover makes a MASSIVE boost on the IM2 total, the film will fall behind. Also, Loki still has yet to prove that he's a truly marketable villain.
New Hulk. The film also has to introduce yet another Bruce/Hulk to the team. Without Norton, it feels significantly less like a crossover and more like an intro ala Hawkeye, and with no other members of the supporting cast showing up, it makes the 2008 Hulk film pretty much pointless. So it seems more like merging the strength of 3 films rather than 4.
The Dark Knight Rises
Advantages:
Popularity. Batman is among the top 3 most popular superheroes ever with Supes and Spidey, people will go see a movie based on his name alone.
The Dark Knight. The last 2D Billion dollar grosser and the highest grossing, most critically acclaimed comic book film ever in pop culture as a lead in helps a great deal, not to mention that the film's ending provided us with a great cliffhanger
Catwoman factor. While some might check in to see how different Bane is from the last incarnation, it's Anne's portrayal of Selina Kyle that will garner the most curiosity.
Trilogy. Usually trilogies equal big numbers for the final film of a franchise.
Nolan. Inception increased his net worth significantly, so his name will have the biggest draw out of the 3 directors.
Drawbacks:
Villain. Bane is notorious in the comics as the guy who "Broke the Bat", but like Loki, he's not the most notorious Batman villain to the general public. Hardy, and possibly Anne, will have to turn it up to try and make a big impact as they're both wildcards. Outdoing Ledger isn't necessary, but they do have to be somewhat memorable.
No 3D. While this may actually be beneficial domestically, it won't help overseas.
Amazing Spiderman
Advantages:
Spiderman. See Batman above.
3D. See Avengers above.
Reboot. As seen with other franchises, reboots usually bring a fresh take to a stale series and can bring in new fans.
Drawbacks:
Marc Webb. This will be his only film outside of "500 Days of Summer". While that was a great film, he is still too green in the industry and Spidey is of a totally different genre.
Origin story. Retelling the origin 10 years after the last one might turn off fans from the Raimi franchise as it will have the "Been there, done that" feel to it.
Raimi loyalists. Although SP3 disappointed, many felt that a sequel could have rectified the problems, so some old fans might not be willing to accept a new Spiderman, especially so soon.
Gwen Stacy. The biggest wildcard out of the 3 films, far more than Bane or Catwoman. While the Joker may be perceived by the general public as "Batman's greatest and most popular" foe, Mary Jane is perceived as Peter's "One and Only" love. Gwen is virtually unknown to the public outside of a glorified cameo in SP3; hell, the infamous scene where she falls off the bridge in the comics has been rewritten several times in film and television with Mary Jane in her place. Also, as much as I hate to say it, the Peter/Mary Jane relationship had massive drawing appeal in the last trilogy, so Mary Jane loyalists may have a hard time accepting her as a love of Peter's life.
So that's it, see you in 2012