To me it's the puzzle first & foremost.
Then there's the color;pageantry and seeing the perefct "running machines" take to the track.
Then watching the one you gleaned out of the pp's start that run at the 3/8's pole; sweep around horses on the turn and collar the leader 100 yds from the finish.
Then the finale.....cashing your winning ticket, with a broad smile, and a feeling of utter accomplishment.

You can't get all 4 of those things gambling on any other sporting event.Occasionally you get the 70yrd touchdoen pass in the final seconds of the football game that enables you to beat the spread. And occasionally you get that third ace on the river. And both of these events are a rush, it's true; but they don't happen very often (at least not as often as seeing your pick come thundering down the stretch, pasing all those in his way).
And in none of the other games of chance, do you have as much to decipher, and as fulfilled a feeling after deciphering.
It's the greatest game.