I dunno...I always thought he was a very average blues player. Whenever I listen to those collaboration cds it always seems that the other guy(s) play circles around him with so much more depth, especially the B.B. King and Eric Clapton one. B.B's got the blues, Eric in my opinion doesn't.
As far as him being a geius during his young years, well what about Page, Hendrix, Beck, Allman, they were all growing up then and I think they all have a lot more to say musically then Clapton.
The only Clapton I can really stand to listen to is the Cream stuff, together they were great, divided they stank.

OK first of all let me apologise for replying to a response which was posted some time ago but i've just picked up on this thread and It's one i'd like to answer because i've been a fan of EC for many many years. The thing I'd say about Clapton is he's been around a very very long time and released an awful lot of material and in that time (inevitably) some of it has been sheer crud. I only have to think back to stuff like Ocean Boulevard and I could curl up and die but by the same token I can listen to the Bluesbreakers Beano album to this day and marvel at the genius of the guy. Let me qualify that last point because you can listen to that album and it's clear that Clapton was still learning his craft and was not as fluid as he would become (which gives me great personal hope) but the point is he was the first real white guy to play like that (some-one is going to come on now and say "oh no he wasn't"). You could probably name many guitarists today who 'might' be better (impossible to prove though I would think) but would they be who they are without Clapton? Even Eric Johnson claims Clapton to be his main source of inspiration and reason he ever picked up the guitar in the first place.

On the point of collaboration CDs I think it's more a case that EC doesn't have anything to prove and let's the other guys 'play circles around him'. Interestingly I've been listening to the new BB King 80th birthday album on which EC plays 'The Thrill is Gone" with him. The way the CD is produced is that BB is alway on the right channel (I think) and the guest artist is always on the left. Listen to the thrill is gone by panning from BB King and EC and I promise you you'll end up with tears in your eyes if you've ever been a fan of BB. The guy just doesn't have the licks or tone anymore whereas EC's playing has as much fire and soul as he's ever had. OK BB is 80 now so we can forgive him but EC is little more than 20 years younger.

Last point. I'd love to agree that Hendrix has a lot more to say musically but sadly I think that's no possible :D (OK I'm being pedantic)

Anyway -Over-rated Guitarist. Sadly I'd have to say Rory Gallagher. I was a great fan as a teenager but re-listening to his stuff now there doesn't seem to be any finesse

Under-rated guitarist? How about Robin trower? Not heard Bridge of Sighs in years but boy did I love that album.

For me though the most under-rated guitarist has to be John Martyn - Brilliant song-writer and multi-talented musician (although far better on acoustic than electric) who has never seemed to get recognition outside of the Uk (and not that much in the UK come to think of it).