They BOTH have many things in common:
1- They both like to be topless.
2- They both have a strong kick, though Phelps' is swimming, Kirk's is flying-leg.
3- They both yell- Phelps at important moments; Kirk, whenever.
4- Assuming that other planets get NBC and are watching the Olympics, they are both now galaxy-class sex symbols.
However, while Michael Phelps broke the world record in swimming several times, Captain Kirk broke through the great barrier at the center of our galaxy, as well as broke through warp 10- despite it being a theoretical impossibility.
Has Michael Phelps traveled faster than light? No.
How about faster than possible? No.
Has he made out with a green chick? Maybe, but not on TV- it only counts if it's on TV.
So, nice try Michael FLOPS, but Captain Kirk remains the Casanova of the Cosmos, the Plasma-Powered Playboy, the Warp-Speed Womanizer.
Congratulations on your gold trinkets; I'm sure you've made your country proud!