I don't think you are right about either of them. Giannis may be one of the Top 50 of all time, but not top 10, and his game won't age well because it is dependent on his insane speed and power, which will fade over time. He will still have a great career by the time he hangs it up and he already has a ring and has a shot at one or two more if Middleton can get healthy soon.
Luka will be right up there with Russell Westbrook, Sam Cassell, Dominique Wilkins, Glenn Robinson, Antoine Walker, Gilbert Arenas and Carmelo Anthony as players who wasted the prime of what could have been incredible careers on stats-padding. Like I said above, last year's conference finals are probably Luka's high point unless he tones it way down.
It is worth noting that he only made the conference finals last year because of a rash of injuries or players missing on other teams.