The other things u have to take into account when cosidering the best is:
Quality of opposition
Quality of ur aircraft
Comparisons between the 2
There were many great German pilots, and many great American and British pilots.....
But Russian pilots had the whole deck stacked against them.... The 2nd leading Soviet Ace flew a damn Aircobra for christsakes.... Against -190's and -109's.... Thats insane, and proves that having 300 kills over some poor, uneducated Russian farm boys flying crap planes who havent even started shaving is not all that impressive...
Get 300 kills in Europe and Ill be impressed to no end....