I wouldn't even begin to know which one is my favorite, since I seem to spend more time nowadays complaining and agonizing over sports than enjoying them.
TBH, I've lately found hockey to be the most enjoyable to watch, but it feels wrong to call it my favorite. I didn't really grow up watching it, and of the four sports it's still the one whose rules and strategy I understand the least. I only really watch it in the playoffs though, which is also the only time I enjoy MLB and NBA. There's just too many games, local announcers are shitty and the vibe is unexciting with half-empty stadiums/arenas.
The NFL is a lot more fun to watch in the regular season since each game feels almost like the playoffs in the other sports, but the length of stoppages and commercials is starting to get unbearable for me. Anyways, gun to my head I'd probably answer your question with football and baseball, but hockey could replace either of those soon
I'm getting better at watching basketball and baseball. Honestly a large part of it is the twins and pups getting better, and probably me getting older.