Yes david and mark are the numbers 1 of guitar
I don't like Roger Waters shows because it's basically like listening to a cover band. Yes Roger is indeed there and singing and his voice is magic but the players around him cannot make it up that is all the guitarists he has
alltogether cannot make up 10% of Gilmour imo.
Gilmour's playing is indeed unique, just like his voice. Very hard to imitate. This being said, it does not mean than other guitarists are bad - just different ! Talking about cover band for Roger is unfair, IHMO. If you watch the "In the flesh" DVD, I think Doyle, Andy Fairwhether-Low and Snowy White are superb guitarists, and they bring a different take. I like Andy's soloing on "Money", SOYCD part VI with John Carin on lapsteel has great energy, like nothing before, with Snowy's solo being great... Chester Kemen and David K. are excellent guitarists too ! I loved the Wall live.
The problem Roger has, is, while he made most of the contributions to the albums concepts and lyrics, he is not needed to reproduce PF sound, as David is. David can reproduce the PF sound with him alone and sessions musicians. Roger's bass playing is ordinary, nothing that Guy Pratt could'nt do, and his voice is... ouch. Ok, pretty unique, but sounds so old ! People like SOYCD with Gilmour's voice only better than on the album actually...