Dragon Ball GT
Better Soundtrack
The music in Super is mostly forgettable and interchangeable to the show while GT's is beautiful and is a crucial part to the show.
Better Art/Animation
Super's art/animation generally average or subpar with only hints of competence. GT, on the other hand, while not as good as DBZ or Late DB is good... on a technical level.
Better Characterization (of pre-existing characters, at least)
With the exception of Vegeta (though he's regressed some), Bulma, #18, and Goten and Trunks all the characters have either been reduced to flanderized archetypes (Chi-Chi, Mr. Boo) or mere shadows of their former selves (Gohan, Videl) while GT gives them a more natural and better (except for Pan and Trunks) progression. Goku isn't a functioning retard, Vegeta actually respects Goku like he did in at the end of DBZ, Gohan is a caring and responsible family man who throws down of he has to instead of a bitch-ass Yamcha 2.0 who spoils his daughter rotten, Videl isn't generic housewife 101, Chi-Chi isn't wife from hell, and Mr. Boo is the jolly and innocent pink djinn that befriended Mr. Satan instead of an unfunny Eric Cartman.
Dragon Ball Super
Better Fight Scenes
In GT the fight scenes are all slow and have uninteresting choreography (not to mention nonsensical) while Super at least tries to make it's fight scebe interesting even if it's still slow and incoherent compared to DBZ fight scenes
Better Original Characters
The only original characters I liked in GT were Ledgic and Nuova Shenron while I came to enjoy most of the characters one way or the other that Super introduced thus far. The only ones I don't like are Botamo and Frost (anime).
No Black Star Dragon Ball Saga
'Nuff said.