Why was the P-51 Mustang the best plane in World War 2?

The Tuskegee Airmen were brought into active combat duty in 1943, the same year as the P-51 was adopted. While the Red Tails were initially equipped with older model planes, by the time they were in active combat, the P-51 Mustang was the premier fighter the USAAF had, replacing almost all other light fighters in active combat.