I don't see why people say he's such a great guitarist. DONT GET ME WRONG, he has some great chops and talent, but I don't think there's anything that unique about his sound.
I love Robbie and think he's incredible. I read your post and wondered what your criteria is for being a "great guitarist"? From what you wrote, it would seem to be that just having a unique sound is what does it? If that's the case, then maybe he's not great. I base it upon other criteria, such as influential and copied they are, how they move me, whether I could do anything close to what they do, how technically proficient they are, how easy they make it look,and yes, even their sound. Robbie has done some amazing things in my eyes and ears and he also has done many movie soundtracks and produced the Rock and Roll Hall of Fame gig during their inception ceremony (among others).
I listen to the Band all the time and Robbie's way of being a team player is incredible, imho. Give the Last Waltz a try.
"The only funeral you should ever try to interrupt is your own, and that should be a full-time job." -Kinky Friedman