The current Warbirds mag has an interesting article where John Fredrickson calls the P-51 "the best fighter of WW II." Maybe, but not so fast, the 51s best feature of long range is not the most vital feature of the entire war.
First of all, the 51 was certainly not the best of 1940 nor or 41, it wasnt even in the war. The Spitfires and Hurricanes, with their pilots and radar had won the Battle of Britain and Spitfires finally won the Battle of Malta in 41 and 42, and it wasnt with 51s. In fact the 51 really wasnt in the war the first few years and didnt become a real factor until the end of 43 when the first Merlin powered B models went into ops.They were not there when the alies flew the missions to Regensburg and Schweinfurt and the bombers were decimated by Luftwaffe, with almost 15% shot down and lots returned with damage and wounded. The first A model with its Allison engine was no match for a 109, nor as good as a Spit Mk V. So the war was half over by the time the first effective 51 came to European operations.
The B model had trouble with engines at first, perhaps a result of Packard changing Rolls Royce design somewhat and making problems, and also trouble with guns jamming when fired in a g loaded turn. But the B was fast and very long range and a big step up from a P-40 or an A model. They did their part in the war and if not as good a dogfighter as a Spitfire or ground attack as a P-47 they were good all around.
And in the last part of the war when very long range escort over water in the Pacific was needed they came into their own. So the 51 was the best long range escort fighter of the last part of the war. And by the way, about 15,000 51s were built and 23,000 Spitfires. And the top RAF aces had 38 and maybe 40 kills, thus half again as many as the top 51 pilots.