I wouldn't say he's "the best," but I think that if things continue the way they're going, Jack White may be considered the last true guitar hero. He's a very good player first of all, and he's also a great showman. For most people, he's the main draw of his band, and a lot of young guitarists look up to him. Just walk into a guitar store, and anyone under 13 buying their first guitar will be playing the one song they know: Seven Nation Army (OK, maybe they know some Nirvana and Smoke On The Water too).
It's hard to say if the game Guitar Hero will lead to more guitar heroes in the future. I mean, when Tony Hawk's Pro Skater came out, nearly every kid in school (myself included) went out and bought a skateboard to try to become a pro skater. But hardly any of us skateboard anymore, at least not the way they do in Tony Hawk's.