For me,
Pre-81:
UNDERrated = Goat's Head Soup (great songs, better "vibe", absolute classic)
OVERrated = It's Only Rock n' Roll (by the numbers by Stones standards; apart from first three tracks, filler)
Post-81:
UNDERrated = Steel Wheels (maybe I'm just attached to this one b/c its the first stones record I ever got, but I've always liked it)
Forum:
Tell Me