Let me throw in my own two cents about the end of the multiverse.
Yes, DC wasn't upfront concerning their reasons for doing so. Marvel was outselling them. Marvel had placed their Golden Age characters all on the same earth as their modern day ones.
Bur aside from Captain America, Red Skull and Namor how many of those Golden Age characters were active? In fact Marvel would years later have aguy named Scurge go knocking off their minor have no clue on how to use them characters.
They didn't need any cumbersome excuse for getting the characters together if they wanted to do so, as did DC with the JSA. A crossover wasn't possible unless it included some character who had the ability to travel between the parallel worlds, like Superman or the Flash or possibly Green Lantern. It wasn't the fans who wanted it simpler, it was the DC editors and writers.
Actaully there were many outs as the resent Crisis on Multiple Earths TPB volumes show. When somebody like the Fiddler can crass between earts by playing a tune and even try for an Earth nowbody at the time even knew about (Earth-3) that this excuse falls flat on its face. By 1973 the writers had a teleporter device that allowed JSA-JLA teams with ease.
Yes, Marv's idea of rebooting everyone post crisis was probably better. In fact, that's what DC is finally doing with their Infinite Crisis. They will reboot 99.9% of the DC line, most books starting over with new #1 issues.
In the end, DC lost more than they gained. The end result of Crisis on Infinite Earth's was that a lot of characters had histories which no longer made any sense, a lot of stories had to be dumped from continuity, and a lot of problems were caused rather than solved. I still recall DC's comments at the time: They claimed they weren't destroying continuity, they were creating it. Fact is, they destroyed what continuity they did have. Zero Hour was supposed to explain all the post Crisis gaffs, but it too fell short.
Crisis on Infinite Earths was supposed to be the solution for all DC's continuity problems, but in the end it only created even more problems. The fact that DC is still trying to sort them out today indicates how wrong they were with it.
Well the problem really was DC had no real detailed plan on what the Post-Crisis universe was going to be like and the resulted was a rube Goldberg nightmare. Furthermore Marvel has similarlly destroyed its continuty with 'shock' stories that make no sence (Harry Osborn and Gwen Stacy had kids? WTF?) and is in its second 'temporary' historical rewrite with House of M. Give the qualityof writers these day and their inability to research DC has no chance at cleaning up the mess it made.