Indeed it is! I love the manga. I have a soft spot for parts of the anime as well, as that is how I was introduced to it. I even watched the Toei anime a few years back which was... sure something. XD But both anime are of a different sort from the manga. I occasionally acknowledge things from the anime, but my fic is my twist on the manga. I did not agree with certain changes or additions the anime made to "explain things".
I've only watched the GX series after myself. I love GX. It is something special. Even if I can't believe in a world where Kaiba would make a school for card games. (I think it is separated by the different series, and then each series has X number of seasons.) But Judai is his own protagonist and despite the storytelling pitfalls, there is lots of fun to be had!
Even if I might have fastforwarded through the duels. The duels don't interest me most of the time. Weird how I'm into YGO when I'm not as into the card game.