Fairness is not on the game, it's on the site. All games can be fair if no one is cheating or manipulating the game. It will just be all about luck, strategy, and how good you are at playing a certain game. But if we're going to talk about a site who's trying to scam gamblers, then that's not fair because you'll still end up losing. Maybe physical casinos are fairer than online casinos because they can manipulate it.
No one will be playing the games if they were not being fair. Yet the house always have the advantages in all these games. Sports betting is the most fair game because no site can manipulate it in any way and the results are always transparent.
Even sports betting can be manipulated. Even before the game starts, they already have a winner.
I think every game can be manipulated if they want to, so I can't say which is most fair. I depends on the fairness of people.