In many ways, it is more game or pastime than sport.
For one, any method of cheating you can get away with to get an advantage is encouraged and often considered part of the game.
pitchers and catchers covering their mouths when they talk so their lips won't be read
using secret hand signs and stealing signs of the other team
using pinch hitters
using designated hitters
pine tar on bats
sliding to hit someone
It also has hilarious terminology.
you get out of an inning by getting outs
If a pitcher throws a ball, you don't want to swing at it
but if you fail to strike a ball with your bat, it's called a strike
It has very interesting behaviors and traditions you won't find in any other sport.
eating sunflower seeds
tapping your feet with the bat
It is a very egalitarian, flexible and relaxed sport for player and fan alike.
foul ball do-overs
keep the homerun ball if you catch it
everyone from 4 to 80 can play
deep rosters and regular call-ups from the minor leagues during a season
different rules for different leagues depending on where you play- one league has designated hitters, the other doesn't
you get three outs and three strikes and four balls
no replay - just umpires and judges who say strange things like 'steeeerike!'
no field is the same as any other - different outfields, different backstops, etc.
no timeouts, just take the time you need and have a meeting on the mound
play 162 games a season (compare to football's 16!)
play other teams in series not just single games all the time
pretty much every town has a ball field
you don't need to be in great shape or wear tons of protection to play
you can play while standing around in a pretty green field on a beautiful day
It has so many ways to get into the game.
baseball cards and memorabilia
relatively cheap tickets
physics of baseball
park and rec leagues
I don't know a great deal about the game so I'm missing a lot. But it's clear there's so much going into the game beyond athleticism.
Go Rockies World Series 2007