GX was good through Seasons 1 and 2.
It was Seasons 3 and 4 that made it tank when the writers actually seemed to LISTEN to people's constant complaints
about it "not being dark enough" and whatnot like Duel Monsters was when GX WASN'T SUPPOSED TO BE LIKE
THAT IN THE FIRST PLACE. It was meant to be a much lighter Yu-Gi-Oh! series for a more "casual" environment
over the fate of the world hanging in the balance in virtually every Arc. As a result of them trying to change things,
the story got messed up, other main characters that were shown strongly before are shoved to the background, girls that
started out strong (like Asuka and Aki) end up being reduced to little more than reincarnations of Anzu/Tea in Duel
Monsters (cheerleaders for the main hero), and newer things that take place have little to no explanation, thus make no
real sense and that worsens things coupled with various retconning or just outright forgetting about them.
5D's started out great and went strongly through the Dark Signers Arc.
Lately though, however, it has gone quite a bit downhill with all the pointless filler episodes and, like GX, is falling
prey to the "Gary Stu" (Crow) who ends up pushing other longer-time main characters to the background a
majority of the time (Aki, Rua, and Ruka). He's basically the Johan of 5D's; minimal backstory, just thrown
into a main character position, Duels seem to be about advertising his cards over actual story involvement, and a bunch
of things happen with him that have NO real explanation to them (like why he was suddenly made a Signer). Basically, the
writers keep retconning things that we've known for a while just for Crow's convenience it seems.
5D's pretty much caught the same sickness GX Seasons 3 and 4 did with how things are going. It's like they
keep dragging out fillers just to buy themselves time to think about what to ACTUALLY do next.