I would preffer flying Me109G over western front or fighting with Zero over Pacific. Because that would be most challenging. After all we all dreaming, right.
Well, I am not going to announce who was the best. We do not have a tiniest idea about fighting in WW1 or 2. Thus I think it is really dumb to us to choose someone over the others. All those guys fought for their cases. Personally I like Saburo Sakai most. He was a real fighter. Think about it...