I've heard not so good things about Seed too, especially Destiny. Does it reach the same heights of so-bad-it's-good?
It's been quite a while since I've seen Seed or Seed Destiny, but as I recall, no.
Seed was actually really good, as I recall. The main thrust of the story (inspired heavily by the original Mobile Suit Gundam) was, Humans and genetically-enhanced Mutants are at a state of cold war, and a supposedly "neutral" colony builds a prototype battleship and five prototype Gundams for the Human side. The Gundams are OP as fuck, for a limited window of time, and then they need to return home and recharge. Problem is, they're too advanced for Human pilots, so only Mutants can fly them. Whoops. So the Mutants figure out that this "neutral" colony is making secret WMDs for the other side, so they plot to attack and steal the Gundams for themselves, but they only manage to steal 4 of them, and destroy the colony in the process, while innocent civilian survivors take refuge inside the battleship. One of the survivors is a Mutant named Kira Yamato (because the colony was supposed to be "neutral", there were people from both sides coexisting), so he gets stuck with the job of being a child soldier and flying the Gundam, which he really doesn't want to do, but he's the only one who can. And then on the battlefield, Kira learns that the enemy leader is Athrun, his old friend from Mutant kindergarten. Kira: "Why are you trying to kill us?" Athrun: "Why are you stopping us from killing the Humans?" So there's a bunch of tension and angst as the 4 Gundams hound Kira and the survivors as they try to escape to safety, while the Human military treats the survivors as expendable, and there's a bunch of heavy anti-war messages. In the end, full-scale war breaks out, and Kira and Athrun are able to stop fighting each other and team up and stop it.
Your mileage may vary on the original Gundam Seed. IIRC it was really popular, but some people hated the melodrama.
Gundam Seed Destiny, I thought was terrible. It picks up right after Seed, but now it has a new protagonist, a horribly unlikable asshole, and his new Gundam is so amazing, it launches in three useless pieces, and then does a midair transformation, to become an ordinary, generic Gundam. Because everything is cooler with useless midair transformations. I think they realized that this new kid they had anchoring the franchise was shit, because halfway through the series they decided to bring back Kira Yamato, and all his friends from the battleship, as if they had nothing better to do and they live for this shit, as opposed to being shoved into it against their will. And Kira is Jesus now, the absolute greatest and most indestructible pilot anyone has ever seen, who kills absolutely nobody because killing is wrong, as he flies around space destroying weapons and ending all wars. It's a terrible sequel, I think, because Gundam Seed never needed a sequel, but Seed was so successful, they needed to contrive some bullshit to shoehorn something else in after it, to keep the money train rolling.
Seed Destiny is not so bad it's good, it's just bad, and it has basically one joke "Jesus Yamato" which isn't a particularly funny joke since everyone has heard the joke already.