Now it looks like Marvel has found people in their cinematic contingent that know what they're doing. The problem is that this never lasts, and large corporations are generally not good at changing with the times.
Marvel has five major problems facing them, and they're fairly significant. Fortunately, there are ways to combat the problems or even turn them to an advantage.
5. The Boredom Factor
The big problem with the larger-than-life characters is that it's hard to both stay true to them and also keep them fresh, especially while weaving a story design that will keep the fans happy. Fans can be notoriously picky, bickering over whether or not their favourite character would act as depicted, or whether the rest of the Marvel Universe would allow the story to unfold based on what they know from the comics. The end result is that the stories cover old ground, the same old heroes fight the same old villains, maybe "reimagined" for the sake of a new spark (much like DC has been doing lately).
The key to solving this problem is inherent in what they did with "Avengers", use the major characters as an opportunity to build more of the Marvel Universe and thus give room to change focus and texture. In movies and theatre, characters define themselves best by those around them, and by sticking with known interactions, stories get stuck in ruts. This does not mean taking characters away from their support structure (breaking up Tony Stark and Pepper Potts, for example) as much as it means finding new people to come on stage (like a Latverian scientist working at Stark Industries on a visa, and now being called back by Victor Von Doom. This doesn't have to be resolved violently, but the fans will undoubtedly enjoy the fight).