When the first issue of World War Hulk was released, I recommended the book. It was that rare modern superhero comic where it contained good character work while containing a whole pile of cool action scenes, including a tremendous fight between the Hulk and Iron Man.
Around the same time, DC began their Sinestro Corps War crossover between the two Green Lantern titles (Green Lantern and Green Lantern Corps) with a one-shot, Green Lantern: Sinestro Corps.
The one-shot was a surprising (to me, at least) success, almost on par with the first issue of World War Hulk.
However, while Greg Pak's Hulk story basically stalled after two issues, Geoff Johns (and Dave Gibbons)' story has only gained momentum.
Part of it is because Pak's story relies on a good deal more contrivance than Johns' story (although we shall see how Johns' story ends, because the odds do seem to be a bit TOO stacked against the heroes, so hopefully we will not get a contrived resolution), including a good deal of "what's the dumbest thing character X could do so Hulk captures him?" writing, while Johns' story has not had to do anything like that so far, and meanwhile, the open scope of the cosmic landscape has ALLOWED Johns to do more.
By the end of the second issue of World War Hulk, Hulk had defeated pretty much every superhero!! The rest of the series was, "Wait for the Sentry to show up" (and yes, his entrance WAS quite excellent), while each issue of Sinestro Corps War has SOMEthing going on in it, like the "Battle of Mogo" (great idea, no?). So even though Sinestro Corps has almost twice as many issues as World War Hulk, it has still managed to maintain the action and suspense over said issues, while Hulk has sputtered out over the course of FEWER issues.
I think the key lesson to World War Hulk, and really, ALL future crossovers, that they can learn from the Sinestro Corps War is - Don't be afraid of having things HAPPEN the entire series - nothing kills a crossover more than the feeling as though issues are being spent merely spinning the wheels without moving forward (yes, I am looking at you, Countdown and Endangered Species!).
Let's hope that the Sinestro Corps will be able to keep it up. And also, let's hope that the Messiah Complex (organized by Axel Alonso) manages to surprise me by being a massive X-Men crossover without spending issues spinning the wheels.