For one of my friends, I would like to buy the full discography of THE best drummer the world has ever seen... but who is it?

It is a guy called Hernandez, who created the song "Born to be alive". Very good drummer.

My suggestion is that you go for Trilok Gurtu, as far as I know he won several best percussion awards and not that it counts, but he definitely sounds very nice and brings several influences in his music.

Ok, thanks guys. And what's about Stewart Copeland (The Police drummer)?

maybe this can help you : http://www.digitaldreamdoor.com/pages/best_drummers.html
it's about rock drummers :-)