Cream and Cheap Trick, underrated? That's a bit of a stretch.
I'll agree with you on the other ones, for the most part, though. Well, actually, just Bon Jovi and Poison. I can see you're not really into the 'classics', huh? That's no problem for me. Or at least some of the more overplayed ones.
Overrated is one of the most overrated terms in history. I think sugaree said that. Well, anyway, I GUESS my votes go to AC/DC, Guns 'n' Roses, Poison, Bon Jovi, Molly Hatchet, and all the other despicable hair metal bands
Underrated - That's easy. King Crimson, Genesis (before Hackett left), Van der Graaf Generator, Renaissance, Magma, Marillion, Steve Hackett, Premiata Forneria Marconi, and Aphrodite's Child.
Edit - Wow. Just about everyone's said that the Beatles are overrated. Interesting enough.