Inevitable after Iron Man 2 was bad in the exact same way that most of the Marvel sequels have been bad.
What is it with Marvel Studios? Do they not see the pattern they develop?
All of their successful franchise have run the same way.
1. Get talented director (Bryan Singer, Sam Raimi, Jon Favreau)
2. Leave them alone
3. Release movie embraced by both comic fans and general audiences (X-Men, Spider-Man, Iron Man)
4. Start messing with director on sequel by shoving numerous b-list characters into it
5. Run off original director (X-Men 3, Spider-Man reboot, Iron Man 3)
6. Release bad movie (X-Men 3, Spider-Man 3, tbd)
7. Reboot franchise
This is only marginally better than their other pattern:
1. Hire bad director (Mark Steven Johnson, Ang Lee, Tim Story, Gavin Hood)
2. Mess with director by shoving numerous b-list characters into it
3. Release bad movie (Daredevil, Ghost Rider, Hulk, Fantastic Four, Wolverine: Origins)
4. Reboot franchise
It seems that Marvel only has the interest of their characters at heart. Their goal seems to be to get as many characters into the public eye as possible so sales of books, toys and t-shirts go up. The movie is nothing more than a vehicle for their properties. Whether or not the movie is good on its own is irrelevant.
Sure, they want to make that first film good. Favreau himself proved that a good movie can make a b list character a list for years to come. But once he did that job, they wanted him out of the way as soon as possible. Directors like Raimi and Favreau understand story. Marvel understands crossovers. That's bound to create conflicts.
Think they will learn their lesson? Just wait until Avengers 2 when Joss Whedon walks off because they want it to star Jack of Hearts and Jocasta.