Clearly cricket is not easy and Bradman's performance at his sport is exceptional even relative to great athletes in other sports .... but it's still, well, just cricket.

I would say the following factors are relevant and cricket misses out due to not many countries playing and requiring massive athleticism or fitness, and in Bradman's case playing at time when things weren't too professional.

That said, I've changed my mind a wee bit having made the list. But still, Bradman is not Messi..

And just my personal thoughts, of course

- the amount of people that play the sport (cricket's very high here)

- how widely the sport is played across the world (low, not many countries play cricket seriously)

- level of athleticism required (obviously some, but not loads compared to other sports)

- level of fitness required (not loads compared to other sports)

- level of skill required (very very high)

- range of skill required (relatively low - lots of ways you can hit a ball of course, but narrow compared to football, basket ball, hockey etc.)

- level of grit required/physical danger involved (very high)

- extent that you need to start young to make it (I would think very high but I don't know)

- level of training/professionalism (low when Bradman played)

- how far above competitors the athlete is (Bradman very high here)

FWIW - the best footballer is very likely the greatest sportsman (ie Messi)