Have you seen anything other than Seed?
I've watched SEED, SEED Destiny, Mobile Suit Gundam (the original show), Mobile Suit Zeta Gundam, Turn A Gundam, Char's Counterattack, Gundam 00, Gundam Unicorn, Gundam Wing, Gundam Build Fighters and Try Fighters, in that order.
Destiny was alright for the most part, but suffered from flashback syndrome, stock footage galore, and a final three episodes that seemed to have been written while under the influence of psychiatric medication. The Strike Freedom is still my favorite mobile suit of all time.
The original show was great; the only one I avidly watched from start to finish without ever taking even a brief break to go watch something else. Excellent characters, decent storytelling, good world-building, etc. It wasn't exceptional or heartbreaking in the way SEED was, but it was solid enough to consistently hold my attention throughout.
Zeta Gundam was a steaming pile of utter garbage. Words are incapable of adequately expressing just how much I
hate Kamille Biden and his absurdly preachy, bitchy attitude towards everything. This is a
shit of such magnitude that when his long-suffering girlfriend comes to him for comfort after her parents have been kidnapped by a fanatical terrorist organisation,
he basically tells her to fuck off because his problems are much more important. After about thirty episodes of enduring his face I skipped to the part he gets violently mind-raped and has to spend the rest of his life as a vegetable. It's
still one of the most cathartic scenes in the entire franchise for me. Oh, and the story goes out of its way to be needlessly dark at every opportunity; characters don't seem to operate under any rational mindset whatsoever and the most frequent cause of death is personal idiocy. The
only good thing about the show is Neo Zeon and the few returning characters from the original - except Katz, of course.
Turn A Gundam is damned good, easily Tomino's best work overall. It's a little bit light on the action for me and the art style isn't really one I favor, but I
loved the Turn A's design and the story manages the impressive feat of delivering Gundam's anti-war message in a manner that didn't chafe worse than a sandpaper condom. I'd say that it's on par with SEED in my personal library, but just doesn't quite have the same 'emotional roller-coaster' aspect I attribute to that series.
Char's Counterattack had good fight scenes and a main character dynamic. Apart from that it was apparently edited by a monkey suffering from LSD withdrawal and every
single Neo Zeon character besides Char Aznable was an underdeveloped pile of villain cliches.
Gundam 00 is not one show in my opinion, but two. Season 1 was excellent; the best 25 episodes in the entire franchise. Season 2 was... nowhere near that good, but still perfectly serviceable. A lot of people claim it was aggressively retooled during the second season, but I don't believe this is true. The plot was a logical progression from the first season that you could see coming a mile off; it just happened to be a lot less nuanced and interesting. The series does have absolutely amazing combat scenes throughout, however.
Gundam Unicorn was awesome. The animation quality blew me away, the story was excellent, the characters had greater depth than the Mariana trench and the Unicorn is one of my favorite mobile suits
ever. I could not have asked for more.
Gundam Wing was also pretty awesome. I haven't watched the whole thing for various reasons, but the first 20 episodes were great. The plot suffers a little from trying to cram in basically the whole UC timeline into a single show, but the characters are nicely rounded. The main issue I have is that the main character is about as easy to relate to as a large breeze block being thrown towards your face.
Build Fighters was absolutely everything I wanted out of a show about animated plastic models, and that isn't some kind of stealth insult. Gorgeous battles, epic finale, great characters and a story that knew how to balance comedy and drama with the skill of a tightrope walker.
Try Fighters was absolutely everything I
hadn't wanted out of a show about animated plastic models. The plot was as generic as a dry biscuit, the characters were one-note caricatures of the originals, the action was stilted, and the allusions to G Gundam
literally made me groan aloud. It had absolutely no idea how to positively homage older series, and felt like a rushed-out cash-in with all the heart and soul of a dead dog.
As for SEED, I consider it the best because it knew how to be seriously dark without becoming pathetically edgy along with it. It didn't pull its punches in detailing just how vicious both sides could be and how the actions of a few deranged megalomaniacs could severely endanger the future of humanity itself. Every breath the protagonists took felt like it had been earned through trial and fire, and every battle had a delicious tension to it that I didn't find anywhere else in the franchise. I loved most of the characters, shed genuine tears on more than a few occasions while watching the show, and found the final battle to be among the absolute finest in the whole franchise. It was truly sublime.