Interesting thread, think I'll do one for my favourite band:
Pink Floyd
Underrated
1) Fearless - A great song with some strong, memorable lyrics and a beautiful bridge. I consider it one of their very best.
2) Alan's Psychedelic Breakfast - Often (wrongly IMO) dismissed as rubbish, it's musically excellent as well as being funny.
3) Fat Old Sun - My favourite of the shorter songs on Atom Heart Mother, lovely to listen on a warm summer's evening.
4) Any Colour You Like - It might surprise some that I've included anything from Dark Side in my list, but I think this is genuinely underrated - I really like the heavily distorted guitar.
5) Mudmen - Excellent combination of Gilmour's guitar and Wright's organ.
6) Nobody Home - One of the best tracks on The Wall, evocative and highly descriptive lyrics about loneliness accompanied with lovely piano and strings.
7) Poles Apart - Really like the lyrics about Syd and Roger, and the central guitar riff. The middle section is weird, but it works.
8) The Nile Song - It rocks! Great vocals by Gilmour, too.
9) What Do You Want From Me - One of my favourites from The Division Bell, it builds really well and the guitar and vocals are powerful.
10) The Gnome - Syd Barrett at his best, a nice guitar line, the lyrics are outwardly child-like but are actually very well written (and amusing when you realise what the song is really about).
Overrated
1) Another Brick In The Wall Part 2 - I like this song, and I really enjoy the guitar solo, but I often see this listed among the greatest classic rock songs at the expense of Floyd classics like Time (let alone Echoes and SOYCD) and it just doesn't deserve that status. It wouldn't make my top five songs from The Wall.
2) See Emily Play - This does nothing for me, this sort of music just isn't my cup of tea I guess.
3) Bike - Creative with some amusing lyrics, but by the end I tend to be glad it's over.
4) Learning To Fly - There's something not quite right about it - it's not bad, and one of the best songs on Momentary Lapse, but I think it seems too commercial and hasn't aged particularly well.
5) Careful With That Axe Eugene (studio version) - The guitar and organ parts aren't quite powerful enough, and the live version on Ummagumma is much better (not to mention scarier).
Picking the overrated ones was more difficult, there are definitely more underrated Pink Floyd songs than overrated ones. I really enjoy Money, and don't consider it overrated.
None of the songs from Animals made the underrated list, it's great album and is widely underrated, but I don't think any of the individual songs are among the top 10 most underrated.
I might do more for a couple of my other favourites, or even bands I don't like quite as much but I think I could do a list for.