Sorry for the late response! But I can indeed tell you why I love GT.
*The opening and ending themes. Easily the best in the series. I grew up with the Latin American dub, which is very faithful to the original japanese lyrics. And they are AWESOME and very nostalgic.
*The drawing quality.
*The designs. Biker Vegeta, Pan, Trunks and even the simplistic design of Goten.
*Pilaf and his gang still being villanous. Also the fact that they, the first "main villains" of the Dragon Ball series, are also the ones who unwillingly kickstart Goku's final adventure.
*The TIME SKIP!! One of the main things I love. Time has actually passed. Characters have grown, and they have changed. Pilaf being presented as an old, decrepit villain still desperately clinging to world domination is the first clue to show how much time has passed since Goku was a kid.
*Uub actually makes an appearance thanks to the time skip. Sure, he's underused, but at least he's acknowledged.
*The music. Simply great. Not a lot of variety, and a lot of tracks are different versions of Dan Dan, but they are extremely memorable.
*Goku being a kid again. One of my favorite points. Kid Goku >>> Adult Goku any day of the week. I love this. You can easily tell just how much fun Goku is having with being a kid again. The episode with him spending a whole day with a pair of kidnappers and causing all kinds of trouble for them is just amazing.
*Pan. I gotta admit that I despised her back when I was a kid. But I grew fond of her. Sure, she's rebellious, annoying and causes trouble. But she's a teenager, and she inherited her attitude from her mother. She's mostly a mini-Videl, actually.
*Goten. I love what they did to Goku's descendants overall. Not a single one of them ended up becoming like him, and I appreciate that. Gohan is the scholar, Goten's personality adapted to the city life (And his friendship with city boy Trunks) and became a guy who is in love and wants to impress his girlfriend.
*Android 18 still being serious and a little rude to Krillin. I'm not really fond of the more gentle, smiling Android 18 from Super. Also, I loved seeing her getting furious and then crying at Krillin's death. I don't know, I found their relationship more "believable" in GT than in Super.
*The sense of adventure, discovery and wonder of the Space/Baby saga. Sure, the second part of the series turns into a series of quick, disposable villains, like a mega condensed tribute to DBZ, but the first part was just amazing. It reminded me of the original DB. Going to new regions, meeting new people, discovering their problems and trying to fix them. That was one of the things that made me fall in love with Dragon Ball in the first place. Trunks getting dressed as a bride, the gang trying to get the Dragon Ball out of a giant's tooth, going into a super expensive planet and being charged for everything....
*Vegeta's family interactions. For some reason, I don't like the "don't touch my Bulma" Vegeta that we got in Super. I actually like the more simple family Vegeta from GT. One that clearly loves his family, but has no issue throwing his daughter 20 feet into the air to "get her to safety". A Vegeta that takes his daughter shopping and then wrecks a couple of guys who hit on her (But with no drama involved!).
*While I do agree that Super 17's saga is kind of lame and rushed, I appreciate some bits of fanservice with old villains (Including Red Ribbon people) escaping from hell and being taken down by the heroes.
*The concept of the Dragon Balls slowly being corrupted after each wish makes a lot of sense, especially with the "you have to wait a year" to use them again thing going on. In the fantastic world of DB, it actually makes sense. A penalty for abusing the wish-granting Mcguffins. I really love that the final arc of the series is about punishing the heroes for abusing the Dragon Balls. Of course this means the Dragon Balls are back into the spotlight, which is great.
*Vegeta's speech about being furious at people wanting to destroy Earth over and over, and being fucking tired of it. Sure, it might not be as impacting as his sacrifice against Buu in DBZ, but it's also a fantastic scene which I consider a followup to his change of heart.
*Super Saiyan 4. Overdesigned? Maybe, but I love how badass it looks. I love how the transformation is achieved, making it more of a side-step rather than a continuation of the golden Super Saiyan line. I'll take monkey Goku over the "Original character do not steal" transformations we are getting in Super.
*The final episode. Man... I love me some closure in my favorite series. I like to think there's an eventual ending. And to me, Dragon Ball GT delivered. At least to my tastes. That final episode is one of my favorite TV moments ever. Very few scenes can surpass the one with kid Goku and old Krillin sparring one last time at Kame House while Roshi watches. I don't care if GT is "not officially canon". To me, this is the end to Dragon Ball. I don't know if Super will be able to pull such an emotional ending, but from what I've seen of it, I highly doubt it.
I'm sure I'm missing some more things, but I've already typed that wall of text.
I understand why people don't like and even hate GT, but those are my personal reasons on why I love it, and why it is part of my headcanon, and why to me, it is the real ending to Dragon Ball.