And I think the whole idea of massive superhero team-ups is stupid, but I'm not going to use that as an argument against JLU.
Anyway, if you've only seen the U.S. version of Yu-Gi-Oh!, the only real redeeming factor is the so-bad-it's-good quality the whole thing has. It plays itself like some "Radical KiRAB Show" that takes itself too seriously and cuts out much of what I found fun about the original.
Is the original Shakespeare? Hell no. Instead, it's more like a classic 80s Shonen series like Saint Seiya or JoJo's Bizarre Adventure, running on its casual use of over-the-top violence while somehow killing off as few characters as possible. Of course, given the whole game theme, the battles themselves also have something of the appeal of Phoenix Wright with the over-the-top back-and-forth drama with epic music playing. The whole thing is so frickin' cheesy and insane that it comes out as awesome.
Now, I also have to say that Duel Monsters was both a bane and a boon to the series. On the one hand, Yugi's Shadow Games were more interesting due to all the crazy stuff he could do to punish the loser. But at the same time, they could also get pretty contrived. Duel Monsters also had the problem that duels could only be held at holographic tables and Yugi no longer got to use the Game Penelty (not to mention Duelist Kingdom seemed to drag quite a bit and lacked the urban fantasy feel of the rest of the series), but after the introduction of the arm-mounted Duel Discs, not to mention some of the crazier stuff that I hear happens in Battle City, the series returned to its original over-the-top style.
Though this is also why I don't care that much for GX: the Duel Academy is certainly over-the-top, but it's not very cool. And from what I hear, Judai doesn't become an Atem-esque badass until near the end. 5RAB, on the other hand, seems to not only put a badass in the lead role, but also takes the series Rule of Cool beyond the impossible by adding motorcycles.