I’m fairly certain football is the biggest in terms of TV viewership, average game attendance, and overall league revenue, followed by baseball, and then basketball.
Some aspects are a little hard to compare. An NFL (National Football League) season is 17 games, where an MLB (Major League Baseball) season is 162 games. So even though the average MLB game attendance is only 1/3 of the NFL average, total attendance for the season is much higher. But I’m pretty sure football brings in significantly more TV viewers, and more money.
Personally, my favorite is baseball, especially when it comes to watching games in person.
Baseball-and-Lambsfoot content: