Honestly, the first film was fantastic and won over critics and fans alike, IM2 has alot to live up too, the cast they assembled for the second film is better than the first film, bring in Cheadle, Rourke & Rockwell in addition to returning members Downey jr and Paltrow, makes this franchise one of the most talented of all comic based films, heck many main stream films would kill for half of them, IMO.
All that said, the second film looks incredible and should easily be surpass the opening weekend of IM1, will in over take TDK, hmmm, have to wait and see, it could, never know. I do agree that the critics will be harder on this film as opposed to the first film, as it has a higher bar to reach for, but Favreau seems to have listened to the fans and amped up the action, so the fans should be much happier there, of course you just can't make ever one happy, just look at the pole question asking what you rate the new trailer, an average of 63% gave it a 10 out of 10, followed by 9 of 10 and so on, yet still as good as it is, 0.9% has given it a 0 out of 10, which absolutely boggles my mind.