My introduction to really good guitarists was at the National Flatpicking Championships in Winfield Kansas... where I attended the first five or six... thus I got to see Doc Watson, Norman Blake and others including Dan Crary and the amazing winner of the 1st festival, Jimmy Gyles.(BTW... Mark O'Conner the fiddler also won the flat pick one year).
   This was only one style, so even though I bought lots of Norman Blake and Doc Watson LPs, I also loved good playing, so when I saw a YouTube of Tommy Emmanuel, I was hooked.,,,because he seems to be able to play anything!
Yes, I found Tony McManus and others, but I really only care for acoustic music. I know OF some of the others noted above, but am not able to rate them.... so the title "Favourite guitarists" was way to broad for me.

Pick 3? I guess if I had to, I'd just list Doc, Tommy & Norman for pure listening.... and that leaves out Segovia and Parkening and other classical ones.

People need to pose easier, narrower questions!