Let us just stop and think over what we mean by "overrated". In my view an overrated guitarist is one who is worldwide famous as a guitarist among the general public, but doesn't impress guitar players much with his skills.
Go out and ask people to give you names of highly rated guitarists, and they will come up with something like Clapton, Hendrix, Segovia, Santana, Hank Marvin etc. (depending on age and musical interests). But to get names like Vai, Satriani, Söllscher, Renbourn you will have to ask guitar players.
Also, what do we mean by a good guitar player? One who can make catching riffs and soloes? Well, in my view these are composer skills. Old friend Beethoven could make catching melodies (to some people) for instruments he never had played.
So a great guitar player is one who impresses by technique and interpretation. When comparing classical guitarist it comes down to this, because they all play pieces written by someone else. There is no reason a rock guitarist should be rated by other standards when we rate him "as a guitarist".
So Clapton has written some nice catchy songs (as a composer). As a guitarist his interpretation is sometimes great. But technically, I am not impressed. A lot of people could make indistinguishable copies of his guitar playing.
Tom