Probably repeating a lot of what others have said but:
Baseball: Much better in person. Just relaxing. Playoff games similarly more fun.
Hockey: WAAAAAY better in person. The starkest difference for me for sure. I find the puck a challenge to follow on the TV and you can't really see the plays develop like you can in person. Plus, TV doesn't really give somebody a sense of just how fast the players are skating and how hard some of those hits are. Further, the fan experience has improved significantly and a Vegas Knights game may be the best in-person fan experience for any sport period.
Basketball: Better in person with good seats but really not much better than TV with not so good seats. In other words, I'm not going much out of my way to go to a professional basketball game unless I am near the floor or in a box. .
Football: Only sport where I'd absolutely prefer to watch at home. I still am big into fantasy football to the extent I am "working" on lineups the entire morning up until game time then I watched Red Zone exclusively. Obviously when one attends a game, one struggles to set lineups and monitor the other games. About a dozen years ago I vicariously had Cardinals season tix (ex-gf's family had them) and, halfway through the season, I found myself just wishing I was at my place watching the games from my couch with my computer open. Football is sometimes tough to follow live and going to the game itself is just such an ordeal. Plus I agree with GM where I just hate the behavior.
Soccer: I need to get to a heavily-attended MLS or Wold Cup game to comment. I haven't been to a live soccer match in a couple of decades at least.
Golf: Here's a surprising one. For a major, TV is probably better because at live golf you're likely going to post up at a hole or tee box and you really don't know what's happening. But, for a non-major, especially if you're a golfer, go get to a tournament and go get there early. It's surprising how close you can get to the players (especially on the tee boxes) and it's a rare opportunity in sports to watch a professional athlete execute something from a literal few feet away. I'm probably one of the few weird ones who strongly prefers to be at the Waste Management Open sober at like 7 AM so I can watch the guys on the range, be at position A on the respective tee boxes, maybe follow a player for a hole, etc.
Other sports:
- Rugby 7s in Vegas is one of the most fun live sporting events I've attended.
- Poker is boring (it's amazing how more tough it is to watch without knowing hole cards and without just the action hands being highlighted)
- Fishing is a big no either way for me.
- Horse racing is waaay more fun in person, especially if you're betting. Almost hockey-level better. Like hockey, you don't appreciate how fast the horses are going on TV and there's just an excitement in the crowd.
- Motocross - More fun in person. It's just loud.
- Rodeo just isn't my thing but it's more fun in person. I wouldn't opt to watch or go, though.