Would not call JP 'great" but he had physical ability, but, he lacked any really good advancement in music theory. He was/is good at many levels but only to a point. You can hear his limits on live shows, where he is going off on riffs, but then just looses it. I think of him as really good, not great. Great guitar is always overlooked and unappreciated.
When you start trying to judge these players ..trying to separate the "really good" from the great..isn't always easy...it's totally subjective..I've gotten in to some heated discussions about who is great and who isn't...some are true technicians and others are just born with the gift...I remember one discussion when the guy was telling me how much better Joe Satriani was than Jimi Hendrix..not IF he was better...that he was way better...and I told the guy that Joe was a better technician...but not better...what Jimi had was natural talent...and some things he did.. were never done before....when you are the creator of something...that's more impressive than the people that study you and "perfect" your creation..