I'd have to say there was/is a LOT of talent in the death metal arena, guys like Trey Azagthoth, James Murphy and Chuck Schuldiner (RIP) also worthy of note are guys like Blasphemer of mayhem, who is a master at writing amazing songs, and warped, complex riffs. I would say that the best metal guitarist is such a hard category to judge, as there are many different styles and genres within it. Hell, mick thompson of slipknot can REALLY play, I have a CD from a guitar mag which ran a feature on him. So another thing to consider is guys (and girls!) who can really play highly technical shredder type stuff, but dont, and focus more on dynamics and the structure of the song in general

my 3 faves

1.Trey Azagthoth
2.Tony Norman
3.Eddie Van Halen