22. "Civil War" by Mark Millar, Steve McNiven and Dexter Vines (Civil War #1-7) – 451 points (8 first place votes)
Mark Millar, Steve McNiven and Dexter Vines reshaped the Marvel Universe for years with this storyline that pitted Captain America against Iron Man over the question of whether superheroes should be forced to register with the government (and thereby trusting the government with their secret identities). Essentially, are superheroes so dangerous that letting them run around without supervision is almost as dangerous as the supervillains that the heroes fight on the street? The question was driven in great part by an incident at the start of the series where the New Warriors get into a fight with some supervillains and the villainous Nitro explodes, killing most of the Warriors but also hundreds of innocent bystanders, including dozens of school children (as the fight took place near by a school). If the Warriors were better trained, would they have known not to start a big fight next a school like that? That's the question that drives Iron Man as he reluctantly agrees with the government and becomes the face of registration (along with Iron Man's then-protege, Peter Parker, who shockingly reveals his secret identity to the world to support Registration).
Captain America, however, feels that it is a violation to force superheroes to give up their privacy, not to mention the fact that he has had enough history with the government not being trustworthy to know that it doesn't make sense to trust it with your secrets. Eventually, Captain America and the heroes who think like him have to go on the run and do their superhero actions as fugitives. Iron Man and Mister Fantastic, meanwhile, embrace their new situation as being part of "The system" by using it to form new innovations (along with some sketchy ones, like building a prison for un-registered super beings in the Negative Zone).
One of the best things that Millar does in this series is know when to let Steve McNiven's stunning artwork just take over, like this sequence where Cap's team sneaks into the prison and gets surprised by Iron Man...or ARE they?
This series massively shook up the Marvel Universe as a whole but especially the Avengers, who ended up splintered into two teams, an officially sanctioned one and a rogue one. Naturally, the government was also soon taken over by the evil Norman Osborn, so Cap's fears came true.
21. "The Sinestro Corps War" by Geoff Johns, Dave Gibbons, Peter Tomasi, Ivan Reis, Ethan Van Sciver, Patrick Gleason plus a whole lot of other pencilers and inkers (Green Lantern Sinestro Corps Special #1, Green Lantern Vol. 4 #21-25, Green Lantern Corps #14-19) – 466 points (12 first place votes)
This epic crossover brought to fruition a number of ideas first introduced during Green Lantern Rebirth (the storyline where Geoff Johns returned Hal Jordan to life and the Green Lantern Corps to existence). Sinestro had returned during that storyline and in this story, he returns to vex the Green Lanterns with his OWN Corps – the Sinestro Corps! The idea of a Corps of yellow-ring wielding villains (chosen because they possess the ability to instill great fear in others) was an amazing high concept and this storyline opened with perhaps one of the most over-the-top thrilling debut issue you’ll see in superhero crossovers.
Kyle Rayner had temporarily been the host of “Ion,” the entity that essentially powered the Green Lanterns. In the debut issue of the story, Sinestro not only removed Ion from Kyle, but substituted Parallax, the YELLOW entity (that Johns had introduced in Green Lantern Rebirth)…
What a stunning sequence. Kyle is transformed into the same entity that he was basically empowered to defeat back in the 1990s, and all while wearing a twisted version of his iconic 1990s outfit. What a way to start a crossover!
This was very much the end of the first "book" of Geoff Johns' Green Lantern run, as the idea of yellow power rings would soon influence the expansion of this concept, into a whole rainbow of colored Corps (that story would ultimately end up in the Blackest Night crossover event). Another major aspect of this story is that it led to the Green Lantern Corps becoming darker and more militaristic - their views on killing, for instance, were ultimately forced to be relaxed to deal with the wife range of attacks that they were suffering form the sadistic Sinestro Corps.
The storyline featured a number of major battles, but the final one, naturally, took place on Earth, with the forces of both armies colliding together on the planet that has given us way more Green Lanterns than any other planet. Ultimately, Johns uses the story to get to a fascinating statement about the power of fear and what a group of people can do when they can collectively stand up to fear. It's awe-inspiring, honestly.