Orr and the Williams' are definitely the weakest. Orr, probably the weakest. I got no real defense. Just feels. Williams' I feel definitely belong on there. Serena has been so dominate for so long and both of them have made their mark on pop culture as well. Right now, you think tennis, you think of them. Well, Serena mostly.
Dale, I don't know shit about NASCAR, but that guy is like a religion down south. He may not have universal appeal, but for that segment of the population, he's as famous as anybody in any sport. Maybe he doesn't belong.
Mickey Mantle though? I won't even entertain him not being on the list. I shan't!
My list would have it a couple ways.
1. Overall super athletes
Jim Thorpe and Babe Zacharias will be here.
2. Athletes who had significant moments that had huge cultural impacts
Muhammad Ali; Jesse Owens (he should be in 1 as well though) /John Carlos-Tommy Smith/Billie Jean King. On a lesser tier for me in this would be the 1980 MOI team/Brandi Chastain.
3. Great Athletes from the big three (MLB/NBA/NFL --- the NHL fanbase is just too small in the Americas) with cultural impact. Babe Ruth saving baseball. Jackie Robinson integrating baseball. Joe D bringing marrying hollywood to sports. Julius Erving inventing the highlight reel and bringing up ESPN's rise, Jim Brown ... just being Jim Brown; Joe Montana making the NFL the king of sports. Michael Jordan and the rise of Nike into a juggernaut.
4. Great Athletes from other sports who transcended the sport. Jack Nicklaus and Tiger Woods made golf way more popular than it ever was before they arrived. Ali obviously fits here as well as does Gretzky and Pele.
I'm speaking more on the Canadian side of North American history but for me Orr is there as he basically changed how defenseman played. He's the blueprint to how defenseman play today in the NHL.
That's about all I have.
I only put it in as an American perspective, because if you brought in Orr, would you have to bring in other NHL oldies into the conversation, the NHL just isn't that popular in the states. Gretzky's here because he made the NHL cool in the states for a bit (and is now an American citizen I guess)