Speed. Paul Gilbert has it like pretty much no one has it.
Its not just straight ahead either. I don’t know if there’s anything that Gilbert can’t play. He runs from one style to another, picking everything impossibly cleanly, impossibly fast, when he has to.
He had to for his first notable band, Racer X. He used much more restraint with hit band, Mr. Big (two platinum, three gold). But Gilbert has the ability to effortlessly play whatever his puts his mind to. He also has the ability to play with feel, to phrase like a blues player, to use a variety of styles, which is amazing for someone that technically proficient.
He is held in high enough esteem among guitarists to join the vaunted G3 tour lineup, and to teach at the Guitar Institute of Technology. Its hard to influence a generation of guitar players much more than actually teaching them.
Gilbert isn’t a guitar player that comes to the mind of the average person, like many on this list, even if they’re successful and have been heard often. But I don’t seem him getting outplayed by anyone anytime soon.