Ok here is my thoughts on it.
Galland-Great leader pilot, all his kills in the west (104) including 7 in the ME 262. Not bad
Molders-Another great leader pilot, 115 kills total (33 in the east), a real innovator in tactics and a inspiration to his men.
Hartmann-A real inspiration to his men, started later in the war when Russian pilots were not so easy to kill, never lost a wing-man. He has real situational awareness in battle to never to lose a wing-man. More kills than anyone else 352 kills all in the east. A real hunter in the skies.
Heinz Baer-220 kills (79 kills in east, rest in the west) He served in France, BoB, East, North Africa, Mediterranean, Western fronts. Alot of pilots excelled on one front and when transferred to another front they had trouble, he never suffered that problem, he excelled on every front. Shot down 16 4 engine bombers, 16 with ME262. This man went from start to finish and did it all on all fronts. He was shot down 18 times during the war.
Erich Rudorffer-222 kills (136 kills in the east, rest in the west only slightly less in the west than Baer) He served in North Africa, France, BoB, Western fronts. Like Baer alot of pilots excelled on one front and when transferred to another front they had trouble, he never suffered that problem, he excelled on every front. Shot down 10 4 engine bombers, 12 with the ME262. This man started in 1940 and when to the end and did it all on all fronts. He was shot down 16 times during the war.
Who is the greatest in my mind? Difficult choice but I think it comes down to two....Baer and Rudorffer in my mind. The others are great also but I think it is almost a tie between Baer and Rudorffer their careers almost mirror each other, kills on each front almost exactly the same. In the end I have to call the greatest ever would be Baer by a hair over Rudorffer.