Isn't Extremis considered one of the best storylines in the IM comics? I'm surprised they didn't go with that stroryline for IM2, which ended up just being an Avengers trailer.
This gets said far too often and now that I've rewatched IM2 a few times (just got the disk after Avengers) it really seems unjustified.
There is one short visit by Nick Fury mid-film where Tony says "Is this about the A..." and Fury cuts him off and brings it back to the main plot. There is the presence of Black Widow which had nothing to do with the Avengers movie except she was in it too; it's like saying Pepper being in the Avengers made it an Iron Man trailer. Then there was the credits scene. That's it. There was nothing past those few seconds with Fury where they didn't talk about the Avengers, that really tied it to the Avengers; it was all about Tony, his despondency about his failing health, his walls (armour) put up against the people around him who cared, his dealing with living in the shadow of his father, and realizing his dad really did think something of him which turned him around.
You're forgetting the penultimate scene in which it's made to look like Fury doesn't want Tony for the Avengers ( even though we all knew how that would turn out
), showing Tony being handed explicit Avengers documentation, complete with a computer screen showing the locations corresponding to individual Avengers on a world map. ( In addition, when Coulson leaves for NM, we're meant to understand that's some kind of S.H.I.E.L.D. thing even before we see the scene after the credits. )