Superman: For Earth was a story I picked up in the dollar-bins some time ago. Great cover. Don't know to this DAY how I read this cover to cover but I needed some injections of speed and oxy-cotton to get through it haha. Seriously, though Birthright is a good story, I think that ranks high on my list as one of the most overrated. I plan on re-reading it soon, haven't read it for awhile. As Miss Lane said, the Silver Age was hit and miss but I never took the Silver Age serious enough to even allow myself to really invest in the actual stories being overrated or not. I usually just read SA stories with a smile of how kooky, whacky and tacky the writing usually is. Once you realize what the purpose was, you read it for what it is.
As for all else, the art is important to me. Some stories are really good but depending on the art, some stories fall flat as vice-versa with bad stories terribly written, but able to get through it with great art carrying the book.