The dilemma with Tiger v. Jack for dominance is Jack took out Arnie, Player, Trevino, Watson and several second-tier hall of fame golfers in their prime (Miller, Floyd and a few others). Tiger never had that level of talent chasing him. Jack's quantity of second place finishes to go with his wins is an incredible accomplishment as well. That said I think peak Tiger from age 25-35 is probably a bit better than peak Jack. Of course Jack had to hit marshmallows using a metal shaft and wooden drivers.
For team sports put me in team MJ and Gretzky. As
@superjohn mentioned, many of us getting old enough and we are far enough from MJ's prime where we are forgetting how dominant he was as a player.
Individual sports for me would come down to Tiger, Jack, Serena, Bolt or Phelps for their dominance over extended periods of time. I've already stated why I'm in the Bolt camp.