The "Avengers" Trailer

"Instead of following the usual blueprint of making a blockbuster and then wringing sequels/spin-offs out of it, they made the “sequels” first by giving each character his own movie with an eye to eventually combining them in one big superhero mega-blockbuster (which itself will have many sequels, of course).
To do it the way they’re doing it here, you need a reservoir of material out of the gate so that you have a clear path from the characters’ individual films to the climactic joining-of-forces down the road. You also need some reason to believe the characters’ individual films will themselves be successful enough to keep the whole project afloat and building momentum towards the mega-blockbuster. Superhero flicks based on Marvel’s mythology are unusual insofar as they meet both requirements."
-Allahpundit, HotAir.com