GX was kinda lame. Besides just generally DISLIKING Jaden/Judai, I just could not get past the fact that there was a school where ALL you learned was card games. I mean, it was almost as ridiculous as the way Pokemon trainers are exempt from school to catch Pokemon.
School of KAADO GAYMU was indeed a stupid idea. They could have made it, so it's just a normal school, but it has clubs based on DM, or some [parasitic bomb].
In fact, there's many other ways the could have done that.
Then there was Kaiba meeting with Saiou and basically not giving a [tornado fang] about him and his goals.
Then in season 4 Saiou blows up the Kaiba Corp building. WHOOPS!