Billy Mills won gold, but that doesn't mean that he had a better overall career. However, I wouldn't slight him in any way, because I admire him a great deal.
Pre was certainly among the best in the world. He went for the victory in 1972, was pushed back by Viren on the last turn, and faded to finish 4th. By any measure, 4th in the Olympic 5000m puts you among the best in the world. He was competing without sponsorship and in poverty against government-sponsored runners from Europe, some of whom were blood doping, as eventually came out when they finally checked for it--and that was the end of the Finnish dynasty in distance running. Pre was also a good deal more consistent than Viren, who competed incredibly rarely--but on the very highest level in 1972 and 1976. In 1975, when Pre died, he was just 25 and at his best, so he may well have medaled in 1976. In other words, he still had plenty of promise and attaining all the American records in an era where Americans weren't competing on a fast European circuit yet and in which Americans were medalling and competitive throughout the distances (Shorter 1972 gold in the marathon, sixth(?) in the 10000, Wohlhuter 2:13.9 1000m and competitive at 800/1500, Wottle gold in the 800m), is a significant accomplishment.