I love Fat Bottomed Girls.
I don't know what songs I'd consider underrated because I think the majority of the "hits" are brilliant.
Lazing on a Sunday Afternoon is a personal favourite. Good Old Fashioned Lover Boy too. Princes of the Universe, Hammer to Fall, Break Thru. All favourites of mine and maybe not the usual suspects.
Overated - of course a lot of people will go for Bohemian Rhapsody, it does divide people but I still love it and always well.
I suppose for me maybe We Will Rock You and Another One bites the dust. But more overused than overated really. They're still great songs but not ones I hit repeat on