Let the holy war begin... again, again and again.
I wouldn't say David and Mark are the best, they have the best sound or touch... maybe... there should be lists for all kinds of those — 100 guitarists with best touch, 100 fastest guitarists, 100 fastest blues guitarists (Hey, Joe!), 100 best guitar innovators, 100 best acoustic fingerpicking guitarists, 100 best jazz guitarists, 100 best gypsy guitarists...
In other words, every one can get his ?1 place in "the best" category, it's just his personal list. Like, "List of 1 best Tommy Emmanuels".
Or better yet — List of "1 best Mark Knopflers" with Mark on the first place. I'd be happy to see that.