Mantle is gold. I don't know how rare the metal actually is, but like William Devane, I would stockpile it if I could. Mantle cards (seemingly) always go up in value, so whenever ebay puts out their 15% off coupons, the first things I look for are Micks. He played a bit before my time and as a New Yorker I've never understood the obsession with him, but the reality is he's at the apex of the collecting world and I don't see that ever changing.
This is a poll thread I started a while back, to try to see how many people around these parts actually saw Mantle play. It may help add a bit to the current discussion...
http://www.net54baseball.com/showthread.php?t=255158