Here are the ones I caught...
Ignoring the fiasco of "One More Day", you have to credit this period of Spider-Man's storyline as one of the worst for him. The Clone Saga was highly regarded as the biggest stumble in Marvel's arsenal until OMD, and it's easy to see why. After investing a LOT of time into proving Peter Parker was the clone and Ben was the real thing, we found out at the end of the storyline that it wasn't the case at all.
It was the first time we realized that following a Spidey tale for several months thinking the title had changed could end up being a big "Gotcha!" at the fan's expense. Quesada would do it all again to us years later.
Batman really hasn't fared as well as you'd think. The first time, Bruce Wayne was crippled by Bane and spent several months in a wheelchair while Jean Paul slowly slipped into madness and turned Batman into an armored psycho. Immediately after he got the cowl back, Bruce gave it to Dick for a little while so he could straighten out some stuff. Dick gave it back, but then picked it back up again after "Final Crisis" and is still Batman today.
I didn't know how it would work to have both Bruce and Dick as Batman at the same time, but I'm really liking it so far. I think it's an interesting dynamic to have Robin as Batman, and have it happening in a real-time storyline.
This was one that I have to give Marvel credit on. They managed to pull the wool over everyone's eyes with the ultimate reveal of who Red Hulk was, and I still think it was cheating a bit to use an LMD at one point to throw Ross out of the contender's list early on, but it worked.
When Banner lost his ability to "Hulk out" at the end of World War Hulk, it seemed the title would take a rest for a while. Wrong. Instead, we got a new colored Hulk who took things to the other end of the spectrum. This Hulk killed the Abomination early on, and showed intelligence and cruelty we hadn't seen before. While Rick Jones might have been the Hulk for a few issues years ago, it was Ross who literally took the Hulk's place while Banner was out of action.
This would have to be the highest-profile superhero death in recent years. Superman's death made the news in the 90's, but the shot heard round the world in the 00's was the one that took Captain America down. The tragic thing was that he had finally be reunited with the one sidekick he thought he'd lost forever just before he was killed.
The aftermath of Marvel's "Civil War" took years to clean up, and Cap's death was sort of the end-note to the initial onslaught. While no one believed Steve Rogers would stay dead forever, it was fun to see Bucky step in and take the mantle. He's changed things around, that's for sure. Unfortunately, he's on trial right now for his crimes as Winter Soldier, so his future with the shield is a little iffy, but there can be no doubt this is one replacement that kept the title alive until the original hero could return.
This was the first major superhero death I can remember reading as a kid. I still remember the exact spot on the drugstore floor in front of the magazines I was sitting at as I watched my beloved favorite hero give his life during "Crisis on Infinite Earths". It broke my little heart!
But then at the end of the maxi-series, Wally West stepped in to say he was taking over his mentor's suit and title. And that's the way it stayed for two decades! To an entire generation of comic book readers, Wally West was the Flash, while the rest of us patiently waited for Barry Allen's return. We saw Batman come and go, Superman come and go, Spider-Man come and go, and a dozen others, but Barry Allen showed up only sporadically here and there.
Then Geoff Johns, giver of all good things DC, brought him back. Wally West was the first sidekick to step into his mentor's shoes and I think it was a great way to use the character. A lot of great things happened during Wally's run (ha! Get it?) as the Flash, but I'm still holding out for good things with Barry's return.
This post is so big (and the choices so many!) that we've had to spread it out to a small series! Join us next week as we hit the next five replacements (including one I'll bet you forgot happened!).