sport isnt nominally difficult, the level of competition determines how difficult it is, and with 9 or 10 nations spanning just under 2 billion people with significantly developed player generation channels it is right up there with any other sport.
the structure of test cricket makes it uniquely demanding in terms of mental strength, to the point where at the highest level, for batsmen mental toughness often can compensate for physical and technical deficiencies (a la misbah), i dont think that is the case for any other ball sport but i may be wrong, maybe pitching in baseball is similar, but not as mentally draining as batting for days.
also re intelligence, dont agree, in any sport the best players tend to have high levels of creativity, awareness and flexibility in problem solving, theres plenty of dumb cricketers out there, pbly on similar level to any other sport.
the only exception being captaincy, however that is becoming even less focused on the individual captain with time.
