A few more I didn't see mentioned (some other names possibly among the best):
Ritchie Blackmore (by all accounts an ass, but crafted many of the sounds/techniques other hard rock guitarists use, and is very versatile)
Robbie Robertson (a very lyrical guitarist, and great songwriter)
Jeff Beck (has played in a variety of genres, hampered by lack of being in a "great" band for very much of his career, and he can't sing either

Steve Marriott (really loved his energy, and a dynamic singer, probably not a "top 10" guitarist, but very good)
I also really love Willie Nelson. His style isn't for everyone, and I wouldn't necessarily call him technically great, but I think his is a singularly unique player.
Agreed with dwccrew, a lot of technically great players don't get the exposure of others (including a lot of session guys who haven't been in regular bands).
And, as some have mentioned, it's all subjective.