Right now I'd say Hayward and Favors, but they have had the most opportunities, and have been able to show what they can do.
Burks got to show a lot last year, but that was mostly off the bench. Hayward excelled off the bench 2 years ago as well. Kanter has shown flashes, but hasn't been able to be consistently reliable, especially on defense.
Burke was good for a rookie, but needs to take a step forward. We'll know a lot more about him after this year. Gobert is a project with great height and hustle, but he needs a few years before we'll know even what his ceiling can even be.
Exum and hood have the potential to be the best of the group, but neither has played in the NBA yet.
Jazz have done pretty well in the draft. I think every pick has the potential to be a good one. Most teams would be jealous of the Jazz success rate recently.