As always in these discussions, it's apples and oranges. If by skill you mean pure "athletic" skill, pool wouldn't even be on the radar compared to boxing, hitting a Major League pitcher, quarterbacking an NFL team, or even golf, where the "perfect" stroke requires far more muscles to work in perfect coordination.
But if you're talking about the combination of talent and dedication it takes to reach the highest level of a sport, then pool takes a back seat to very few others. Steve Mizerak could never compete in an Olympics high jump, and Michael Jordan wouldn't win one set in a thousand against Fedor Gorst, no matter how much he practiced.
And I don't think it's any accident that the very top players of the past few years are nearly all in top physical condition. How could they remain at the top, day after day, week after week, month after month, year after year, if they weren't?
To make another comparison, are ballet dancers athletes? By one measure, they're at the top of the any list, with perfectly trained and hardened muscles, world class hand-eye and foot-eye coordination, timing that rivals a Major League hitter, and being able to live with the mental pressure that knows that one slight misstep can ruin an entire performance.
OTOH how many ballet dancers could execute their moves if a team of rival dancers were trying to knock them on their ass?