Civil War is the best crossover ever. In fact, I began reading comic books almost 20 years ago, and I have long expected something like this to happen.
First, because of the changes. Changes are not just cosmetic, such as characters dying, returning, joining groups or getting a new suit. The whole superhero genre was reformulated, as it had never been attempted before. Superheroes would no longer destroy everything, fly away in the night and return to the safety of their secret identities: the options are either to follow military discipline, live always on the run, or give it up.
Second, because of the approach. It is not the first story with a Super Registration Act
, but it's the first that doesn't use the "heroes = good, government = evil" angle. As if superheroes destroy your house fighting for the American way of life, and you had just to smile about it. I particularly enjoyed the meeting of Sally Floyd and Captain America: if I ever met Firmenich or Che Guevara, I would tell them similar things.
Third, because of the ending. With no good vs. evil angle, it was not immediately obvious how would it end. In fact, someone would have suspected that Cap would win, to keep the status quo. Not only it did not end that way, but the battle was not ultimately won by Iron Man, but by The Real Heroes
. How often does than happen?
Forth, there was a detailed insigth into each character and their reasons to be at the side they were. Everything was fine, and made perfect sense. Specially for both leaders, with a visible conflict between their personal friendship and their view of the world. The issue when they tried in vain to settle their differences at the abandoned Avengers Mansion was one of the highest points of the story.
It is obvious that the story takes place in the context of the 9/11 and the Bush administration, but I don't see a problem with that. "Watchmen" and "The Dark Knight Returns" are widely acknowledged as the best comic books ever, and the Cold War is crucial to their plots.
If there was something wrong with it, it was that Marvel eventually backed off and returned to the standard superhero genre. That day, I ceased buying comic books. But Civil War and its aftermath was the best thing that I have enjoyed to read in comic books.