No one knows, because no one ever talks about it.
For a game that can be accurately described as “hit a ball from here into that hole with a stick in as few shots as you can”, golf sure has a lot of rules. I own a book called ‘Decisions on the Rules of Golf’ and it’s an inch thick.
Lots of mention of American football as the most complicated. I know absolutely nothing about it so can’t really comment. But among major sports that I know just enough about to always be befuddled, I’d consider baseball to rank up there with some of the most complicated rules and strategies. Conversely, I think the basics of hockey can be explained simply enough that even a novice can enjoy the game after a very brief introduction.
There was, to be sure, some apparently arcane complexity on the occasion when Brett Hull scored the winning overtime goal for the Dallas Stars against the Sabres, in the third overtime of Game 6 of the 1999 Stanley Cup finals. The Stars were celebrating their victory on what appeared to be a valid goal – not just any victory, but winning the Stanley Cup in triple overtime. There was just one small problem. The NHL at the time had a rule that a goal didn’t count if any part of the goal-scorer’s body entered the crease – the blue area in front of the net. And, as the Stars’ Cup celebration was well under way, video replays showed Hull’s skate very clearly in the crease. Leaving NHL officials with a big dilemma. Which they resolved by declaring later that the crease rule didn’t apply if the player had “possession and control of the puck”. A bit of hockey-rule subtlety that was especially notable for the fact that no one had ever heard of it before! 
There’s also the fact that hockey culture calls for a detailed play-by-play, which helps those who may not always grasp what’s going on. Whereas ISTM that in baseball – and I’m speaking here as a baseball ignoramus – the culture is for very laid-back sparse commentary about game action, seemingly under the assumption that everyone just saw and understood what happened, so no need to describe the obvious. Instead the commentators seem enamoured of “color commentary”, which basically means reciting statistics rather than calling the plays, and by golly, no sport has more statistics than baseball!
There is perhaps some value in differentiating between the rules of the sport and the rules of the league structure.
One thing is for sure; it has the LONGEST rulebook of any sport I know of.
Perhaps horse racing has just as many, if not more. I don’t know for sure, but I’d say that horse racing ranks with baseball in terms of number of statistics.
Baseball probably has more stats than horse racing, if only because of the larger number of events.
I wasn’t considering scoring as part of the rules of the actual game, but I guess it has to be taken into consideration. Beyond that, however, the only real “rule” is to roll the ball down the lane and knock down as many pins as you can without crossing the line and fouling. What else is there, really?
Following the bowler’s dress code.
The bowling thing makes me think of judging sports by the “5 year old” rule. Namely, if you have a 5 year old trying to play the sport, how many times will you have to instruct the child on the rules before they play the game correctly?
Bowling scores well under this metric, though you will have to say “it’s your turn” and “you’re in that lane now” pretty frequently.
Darts are dead easy, though I wouldn’t want to be near a 5yo boy with sharp things to throw.
100M dash I think is also 5yo friendly.
You couldn’t pay me enough to try basketball. No, you can’t run with the ball, keep one foot planted. One… plant one foot unless you’re… stop running.
They can’t even teach that part to players in the NBA.
They could if the referees would enforce it.
You couldn’t pay me enough to try to enforce that rule in the NBA.
Obviously, you would need the spineless execs of the NBA to back you up. Good luck with that.
“OK, now do it again, to try to knock down the rest of the pins. Good, that was a good try. Wait, no, don’t do it again, now you have to wait for the machine to reset the pins.”
Yeah, it’s definitely simpler than football, baseball, or basketball, but it still has its share of rules.
And I think that basketball and football are both simpler than baseball, at least in their fundamentals. There are a lot of details beyond this, but basketball is “Try to get this ball through that hoop”. Football is “Try to get a guy on your team in this part of the field, with control of the ball, or failing that, try to kick it between those poles”. Baseball is “Try to hit this ball that’s thrown at you with this stick, and then run to those sandbags in order, without someone tagging you with the ball while you’re not in contact with one of the sandbags”.
A five-year-old would probably need help with the math, and possibly a reminder that the bullseye is not the highest score on a dart board.
Sure. Scoring (how you determine the outcome) is essential, but recording (“was that a hit or an error?”) isn’t.
Wait, it isn’t?
And come to think of it, the layout of the scoring region of the dartboard should probably be considered part of the “rules of darts”.
I still say it’s the hundred-meter dash, or other similar races. If you take someone ignorant of sports, from anywhere in the world, and tell them “Set up a running race over a distance of 100 m”, they will all, 100 times out of 100, come up with functionally the same event.
A bullseye is worth 50 points.
Hitting in the 20, 19, 18, or 17 area, in the “triple” ring, will yield more than 50 points.