Its better to read other threads in comparing who's better, like Hendrix vs Cobain, Clapton vs SRV, Hammet vs Dime, etc, since those topic are subjective and opinions are always right whoever you think is better.
But in this case, this thread can be proven by facts and figures, we can calculate the fastest so why debate on it. Whats worse......the fastest is always mistaken or even considered to be the best by others. So dudes I think we need a conclusion to all of this.
The Fastest credible guitarist right now is FRANCESCO FARERI. (Marcus Paus and Mr Cucumber is a hoax, Its proven to be edited and SPED Up.) He is definitely the fastest guitarplayer but certainly he is NOT the Best and its a bunch of $#*% Crap. The Fastest and the Best are two different things. I hope some aspiring guitarists hoping to be good would realize that.
Proof ? >http://www.francescofareri.com/fareri_shred2.wmv
Guitarplaying is 1 Percent Inspiration, 99 Percent Perspiration... :)