Trillionaire, baseball is probably the sport most prone to arguments - there are so many statistics and it is, compared to the other North American major sports, very old, and your average fan is probably a bit geekier. The consensus far and away is on Ruth.
You can argue that other players had more physical talent (like Willie Mays), or would have been comparable had they had better luck with health (like Mantle), but I don’t think anybody in a North American professional sport ever stood head and shoulders beyond everyone else in his time the way Ruth did. He was the first and greatest giant of his sport. Jordan was the best basketball player, but at least there were people who could compete with him. In 1919, Ruth became the first guy in baseball to hit 28 home runs in a season (he finished with 29). Doesn’t sound so impressive? The next year, he became the first guy to hit 30, 40, and 50 in a season (ended up with 54). In 1927, he was the first guy to hit 60 - more home runs than any other team in the league.
Early in his career, was the best pitcher in the game (I think he still holds the record for wins in the World Series), and he became the best slugger. He took over the all-time career home run record in 1921 with his 139th. When he retired, he’d pushed it to 714 - and the next closest guy had 378.
Granted, these days the average athlete is much better, so excelling is that much harder. But Babe Ruth is synonymous with his sport for a reason.
I’m not sure what sport you’d associate Babe Diedriksen Zaharias with (she was a champion golfer among other things). Jim Thorpe is among the all-around greats. I’d take Navratilova in women’s tennis, in men’s I’m less sure. You can make a case for Pete Sampras, and probably a better one for Rod Laver.