I agree with King Elvis about Michael Anthony. Thinking hard, I can think of maybe ONE improv-ish run on a VH record? (Towards the end of "In a Simple Rhyme," right after Dave goes "ow!.....whoa, yeah-eah...")
I also agree with the King about Gene Simmons. He does more than one would expect, especially considering you can figure out most of Paul and Ace's riffs on air guitar.
Other folks I think are underrated include John Paul Jones and Geezer Butler.
I was overrated every time I got off stage and had someone come up to me and say "Wow, dude, you're an AWESOME bass player!" Maybe--compared to Sid Vicious or the guy from Foreigner
"Those who would trade their essential Liberty for a perceived temporary Security deserve neither Liberty nor Security." --Benjamin Franklin