MLB was the most popular sport from the Babe Ruth days thru Joe D, Yogi, Mantle, Maris and even into the 70's with Reggie. Maybe it was the Super Bowls between the Steelers and Cowboys that got the NFL's popularity on the upswing. By the 80's the NFL had caught and then eventually passed baseball as America's most popular sport. Over the last 30 years the league's popularity as exploded. Today the NFL is way more popular than any other sport and it's not even close. As for the NBA I don't think basketball was ever as popular as football. Baseball was more popular at one time but not anymore.