There was a good quote from a Team Sky (cycling) coach/science type on this a while back - interview asked him what he thought the difference between professional cyclists and normal people was. His reply was that physiologically, probably 90% of the population could make it as a professional (given dedication, training, coaching etc). However, only the top 1-2% would ever have a chance of winning anything, rather than just being a team support rider.
Natural talent is probably more important in cricket than most sports, but the example probably carries over - most good club players probably have the reactions/physiological attributes to play top level bowling given the training etc, but it's the practice, coaching, and (importantly) mental drive that separates the professionals from the rest of us, and then only the very very best of the pros make the step up to international level.
There was a really interesting study into the difference in reaction/decisions between top batsmen/average clubbies when facing quick bowling, but I can't find it again. As I recall the basic conclusion was that the reaction times are not significantly different from pros to ams, and the difference in performance was down to unconscious reactions as you can't react quickly enough at those speeds of bowling. This would seem to imply innate ability is key, but is pretty open to interpretation.