Each people has their own opinion. There's a tons of people out there are also say that GT is good, they love it. For me I only like the design of GT character, all of them has an originality, never before seen design. What I hate about GT is the presentation of it and making Goku a kid. Toei ruined it. The idea of Baby being the last survivor of Tuffles seek revenge against Saiyan and the Dragon Ball itself became their enemy in the form of Shadow Dragons was actually a pretty dope idea. It just it wasn't present it well. For Super 17 arc, that was actually a good point to bring back Future Trunks, but they screw up, and Super 17 is indeed the worst arc in the whole DB franchise, I also agree on that. I'm personally wanted to see Baby arc and Shadow Dragons arc get re-create back in DBZ/DBS style (like Baby possessed Vegeta body, but this time with his God Ki and SSB for Baby to use, and the Shadow Dragons will have a connection with the Zarama, the creator of Super Dragon Ball, just some idea). For me this two arc has potential. Toei just wasted the opportunity.
Now let get back to the topic, this is just a video game. We don't have to take the story seriously and just play with the character. The more character are better. That was many DB community being asking for DBZ games. That why they praise Tenkaichi 3 until now. Plus the story they present in Xenoverse is a new twist for the story that we know, so it's not gonna hurt whether the original story was good or bad for us.