Most of us on this site have watched a lot of basketball, and if you've watched a lot of basketball and you don't think Luka has "it," I don't know what to say.
The kid isn't just making stellar plays - he makes 1-2 plays a game that make the crowd gasp, he is already one of the top 10 clutch scorers in the league, currently ranking 6th by the numbers, just behind Kyrie and with the next three guys being Lebron, Paul George and Kawhi.
The Mavs have gone from a 24-win pace to around a 40-win pace. He's a winner and the only thing that would keep him from becoming All-NBA and more would be an atypical early plateau. Even if he only gets a little better, though, he'll be a perennial All-star.
Tatum on the other hand is in the "talented with a bright future" category. He's about as promising as the top 3 guys from a normal draft class. Nothing to sneeze at, but at this point we don't even know whether he will hit All-Star level for sure.