To me it's not a contest and I have no favorites. They all have different styles and I very much enjoy listening to them all. And as Erik pointed out, there are some important trumpeters David missed (bound to happen with only 10 choices). Who do I listen to the most? Miles Davis, Harry "Sweets" Edison, Freddie Hubbard, Lee Morgan, Chet Baker, and Roy Eldridge. But I wouldn't necessarily call them my favorites. I just love their music.
Clifford Brown was arguably the greatest technical virtuoso on the trumpet. His early death was a tragic loss for jazz. I listen to his music frequently, but because he died so young he did not leave a voluminous recorded legacy.
--Jerome