Well, I'd have to make lists of 5, not just 5...
Top 5 Classic Cartoon Actors
Mel Blanc
Paul Frees
Don Messick
Daws Butler
Bill Scott
Top 5 Current Actors
Billy West
Jim Cummings
Rob Paulsen
Charlie Adler
Frank Welker
Top 5 Actresses
June Foray
Tress MacNeil
Kath Sourcie
Russi Taylor
Nancy Cartwright