The F-16 development and design was unique in both its objectives and the role expansion capabilities over time. It was the first USAF air superiority fighter developed for that purpose since the F-86 - a 30 year lag. While the Soviets developed fighters we were developing 'weapon systems'. Even the USN fell into the trap after the F-8.
The F-15 was much bigger simply because the long range, high powered radar required a large dish and ate energy ravenously.
The F-16 (and F-15) comparatively speaking was a very 'hot' climber and turner and energy manueverability hound with both internal 20mm and excellent air to air (finally entering a reliable phase of maturity) missiles.
The P-51 was designed to fly fast, turn and climb - but perhaps never outperforming more specialized fighters. It was an all purpose machine that matured into the long range/high altitude air superiority fighter by virtue of finding the right engine to maximize its inherent aerodynamic performance - while the F-16 was that from the beginning, and it matured into a capable strike fighter.