Expanding on a comment ("Each year, I hate the end-result of Crisis a little more (even if I genuinely loved the story itself)") I made on someone's post yesterday:
I LOVE Crisis on Infinite Earths, but the outcome has sucked for decades. The initial outcome -- having the Earth 2 JSA/All-Star Squadron adventures take place on Earth 1, is mostly fine by itself.
But right away, we had the problem with the Continuously-Published Five: Superman, Batman, Wonder Woman, Green Arrow, and Aquaman. Since their Golden and Silver Age versions were the same (as far as secret identities, overall origins, etc went), they couldn't both exist, so the Golden Age versions were excised (and new heroes were invented to retcon past stories). This also applied to a handful of other Golden Age characters DC brought into the fold (Captain Marvel and Plastic Man both come to mind -- Plas as the FBI liaison to the All-Star Squadron was fantastic).
But that wasn't as bad as Problem #2, which was the changes made to modern heroes (Superman never was Superboy, Hawkman is a modern hero just coming to earth, etc). This in turn impacted associated characters, so Power Girl was now somehow tied to Atlantis (until she wasn't), the Golden Age Hawkman was also the Silver Age one (until he wasn't), the LSH (don't even get me started), etc.
But even that's not as bad as problem #3. While the Earth 2 Golden Age stuff mostly still existed, there was a HUGE amount of contemporary Earth 2 stuff that was lost. We had Batman dying, Dick Grayson becoming the new Batman in a way that mattered (not like the crappy interim plotlines we've seen periodically), Huntress being Batman/Catwoman's daughter, Black Canary and Red Tornado moving between Earths, etc. And of course, the entire concept of Infinity Inc as essentially the only group of contemporary heroes on their Earth loses meaning when they merged and became instantly less relevant than The Outsiders or The Forgotten Heroes.
Needless to say, almost every effort to try to "fix" these problems has gone from bad (Infinite/Final Crisis) to "Scott Snyder must have blackmail material on someone" (Dark Knights: Death Metal and Infinite Frontier).
Anyway, while there have absolutely been some fantastic books since then (including ones like Morrisons' Animal Man that built on Crisis), the actual DC Multiverse structure as of 1982 was still better than anything since.
