Hmm. Well, I guess that's as good an answer as any.

I think that I hit my stride in really starting to enjoy my comic book reading during the late 80's and early 90's.  After having read steadily (at that point) for two decades, I think I reached a point where some of the storylines -- even from wildly different titles -- really started to seem derivative of one another.  DC and Marvel each wanted to have their 'event' titles annually, and that seemed to go back and forth between a very small roster of key superheroes.  But -- I've read loads and loads of Batman and Superman comics, mostly -- I think there's only so much you can do with any character.

Now, I do remember reading a few titles when I was younger that stuck in my brain, and I recently sought a few of them out thru ebay sellers, picked 'em up, and reread 'em, and I experienced a bit of a disappointment, maybe something like what you did.  I couldn't say why.  I think it was just that I had a smaller worldview when I was younger, so some of the minor quibbles of plot and nuance weren't as easily identifiable, unlike today where I picked up on them right away.

Age could be a factor in the equation, though.  I just tend to think that it's more 'life experience' that impedes one's ability to look at these things the same.