Most successful, yes.
But producing is such a broad topic.
There are many claims to the title for different reasons.
Most successful: Dr. Dre.
Best Run: Dr. Dre (NWA, D.O.C., Chronic, Snoop are all classic even iconic albums)
Best sample flipper: DJ Premier isn't the typical looper and will chop a sample beyond recognition.
Most influential: Dr. Dre is to Hip Hop production what Michael Jordan is to the NBA, what Michael Jackson is to music in general
Best Drums: Timbaland hands down
Best mix: Dr. Dre
^^^ IMO.