Skateboarding belongs.
Rock climbing really belongs although the format will not crown the greatest climber since they added speed climbing as a component. The world's best trad/lead/boulder climber is easily among the world's best athletes both physically and mentally.
After moving to California and embracing the "cowabunga lifestyle" I've been surfing, climbing, skating and backpacking a ton in my late 30s and early 40s. Even though skating is the only one I had prior experience with it is the hardest of the four, the one I'm worst at, and because of injury risk the one I officially "retired" from. Hoping to do the others at least another 15 years.