You'll undoubtedly know about Boelcke and Immelmann, but here are some men who had their first successes on Eindeckers, or became aces on Eindeckers.
Ernst Hess (first victory in Jan 1916, with help of Boelcke, 17 victories total)
Ernst Freiher von Althaus (except for one or two of his official score of 9, he scored his kills on Eindeckers)
Kurt Wintgens (fell in combat on Sep 25/26 1916. 19 Victories, most in Eindeckers)
Walter Hohndorf, Max Ritter von Mulzer and Otto Parschau probably scored the majority of their victories on Eindeckers.
You should also look into
Wilhelm Frankl, Hans Berr, Hans von Keudell and Stephan Kirmaier. Maybe next week I have some more names.
Boelcke was probably the greatest Eindecker ace. From what I've known he scored his first in a 2-seater LVG. Then numbers 2 through 19 in various Eindecker types. Number 20 was in a Fokker DIII and I think the rest was in the Albatros DII. 18 Victories in an Eindecker.... Runner-up would be Immelmann or Wintgens (my bet would be Immelmann).
Kind regards,
Reinout