I trained at a cross fit gym for 3 months. In general the people that do it consistently and aren't naturally heavy or bordering on obese are pretty damn fit.
I noted a few things though.
I did not try out for sports in high school because I wasn't interested in team sports. I was highly into bodybuilding at the time though and always possessed a solid level of natural athleticism.
Within 2-3 weeks training at the cross fit gym doing my "own" workouts I realized I could thrash most all of their most fit guys in their workouts if I wanted to.
Cross fit to me is doing a well rounded program with emphasis on cardiovascular demands and neuro-muscular coordination.
Saying these guys are superior to most is kinda wrong imo. A good lifter that lifts hard and heavy on a solid program and does a reasonable amount of base cardio within a week or two of adapting to the cross fit endurance workouts would do extremely well. I know this because this is basically what I did. I went from a basic lifting program to doing lots of kettlebell work, jumping, pullups, rope climbing and running with minimal rest times and watched alot of the workouts and checked out top scores at the gym.
You can literally achieve the same aerobic effect doing a standard gym workout by limiting or completely foregoing rest time between sets and exercises. Granted, you need to be focusing more on compound movements to generate enough oxygen demands, but the net effect is similar.
I have nothing, but respect for cross fit training. It's fun, it's balanced and you'll look good and perform well all-around from doing it, but cross fit is it's own deal. Doesn't make it better compared to every thing else.
I personally would rather be strong as hell and do 20 minute fairly intense cardio 3x a week and have a reasonable cardio base while being able to display alot of strength/power then have the cardio capacity of a marathon runner and the physical capacity of a moderately strong person.
Also using a few particular athletes as great examples of cross fit doesn't really prove much. Those guys are genetic specimens and probably gifted athletes regardless of what they do. Both guys could probably bench 200lbs or more the first time they every touched a bench.
I have known a few genetic freaks that didn't even train and were stronger and better looking than 99% of the guys in gyms. I certainly wouldn't use them as examples except to point out the freaks they are.
Just my opinion.
I'd also like to mention that you can literally be cross fit by working a manual labor job. I worked in excavation for 6 years and not only did I operate, but I pushed more shovels, swung more picks and sledges and operated and carried more jackhammers and carried more buckets/bags of gravel than most people can imagine. A job like this combined with some basic running/rope skipping for high level cardio damn near literally equates to cross fit training.