I can think of at least two players who are more generally considered the greatest in MLB history, and neither was ever a Yankee. There are about 1,000 other clues you could give for Ruth.
To be sporting, I think there are two possibilities other than Ruth: Willie Mays, the most "complete" player ever; and Ted Williams, the best pure hitter ever. Mays was a superstar fielder (12 Gold Gloves), runner (four-time stolen base leader), hitter for average (.301 lifetime average, and 3,260 hits, 13th-best all-time), and hitter for power (660 home runs, sixth all-time). Probably the best combination of the "five tools" of anyone who ever played. Williams lost four seasons of his prime to fighting in World War II and the Korean War, but still topped 500 homers. The last player to hit over .400. Highest career on-base percentage of all-time at .482. Six-time batting champion (including at age 40). His OPS is just a hair below Ruth's. But if you consider power hitting the most valuable skill in baseball (which it is), it's definitely Ruth. He was also an ace pitcher, of course. I think Mays's argument is more compelling than Williams's...but it's still Ruth.
Babe Ruth is number one on almost every list.