Crisis on Infinite Earths

It's rare that a comics crossover series actually lives up to its own hype about how world-changing it would be, but the Crisis lived up to that hype at the time. Prior to it, DC had a multiverse - a bunch of different Earths, each with their own stable of superheroes and villians. Then the Crisis happened, and DC was left with one Earth, with all of those heroes living on it, and central characters like Superman, Hawkman, and Wonder Woman had their histories completely rebooted.

I can appreciate the concept of a multiverse; from a writing standpoint, it gives the writers at DC comics an opportunity to tell a bunch of different types of stories with a bunch of different characters. My problem with it, though, is that in practice you end up with a bunch of different Supermen and Supermen analogues, and essentially the same stories beiing told with different window-dressing. It seems like a waste of a great concept, so I like the fact that they tried to simplify that into a single timeline. My first exposure to DC was all post-Crisis, as well, so the whole thing just seemed convoluted.

Of course, now DC's back to having a multiverse again, so the entire thing's been rendered moot.