Adolphus "Sailor" Malan vs anyone.
He took Werner Mölders on a quick spanking lesson where Mölders actually did everything right by the book (getting on Malan's tail after loosing a squadmate to him).
In that case, the element of surprize "kill" was gone, so it was a pure dogfight.
Anyway, Marseilles was good, but it was also tactics. He did the shotings in some peace because of good cover, but he was good allright.
Rall will say that Marseilles was the best, however some LW guys "whispered" to me that Rall was the better shot, since he was renowned for making kills under high-G, - quite the opposite of Marseilles who would make his kills near to a slow speed stall.
And nobody mentioned "Screwball" Beurling......
There were so many good, and it depends on the rides as well. The question here is a tad open..