Obviously, it will depend entirely on Precisely where you are referring to:
For instance, where I come from in Victoria, Australia, they would barely have heard of baseball, and very little soccer was played here at all in those days:
Here the most popular traditional sports were cricket and Australian Football, yet just over the nearest state border, in NSW, it would have likely been cricket and rugby.
Cue sports, such as billiards and snooker also became more popular around these decades. Boxing was also a big one back in the early half of 20th Century. Martial Arts were virtually, unheard of ... basketball barely touched ... soccer only English 'die-hards' - In Australia, mainly cricket and the football codes, some tennis ... and horseracing has also always been big in Australia.
the most popular sport was baseball
Baseball was because it was America's sport in those days
Baseball was United States most popular sports going in 1920s. Players like Babe Ruth played an important role in making it a fan favorite sport. Ruth went on to make New York Yankees a force to reckon with in MLB.
In the US it was baseball.
Football is the most popular sport in Brazil.Soccer.The most popular sport in Brazil is football.
Baseball must have been one of the two. I can't guess the other.
This is any easy question..... The most popular sport by far during the 1920's was baseball. This was around the time when most of the "Big Players" started to appear.
cricket is most popular sport
Yes, tennis is the 4th most popular sport in the world, 13th most popular sport in America, and the most popular individual sport in the world.