As I said to Pro earlier, I think the Avengers is also gonna be a tougher to sell name, mainly because a lot of people will relate it to the other version of The Avengers with Steed and Emma Peel etc, which is probably why they are doing a bunch of solo films initially, and have tagged the Cap movie with the First Avenger tag.
Iron Man was probably lesser known than Cap, but obviously the name Iron Man is a whole lot cooler and Superheroish than Captain America, plus it had all the special effects hype.

The one thing Cap has going for it by releasing it as a solo movie, is that there is a lot of hype for superhero movies at the moment, so a solo movie is less risky right now.

If nothing else, we have seen that launching characters out of team movies, doesnt necessarily work.
Other than Wolverine, who in the X-Men movies did people want in a solo film?
Probably nobody.

The problem with team movies is theres too much of a chance of one or two characters getting all the screen time, and everyone else ends up looking like Lois Lane or Alfred.

Snarf is shit. His death will be rejoiced!