I've watched the whole series of SEED, Destiny, and read as much of the Astray series thats been released in the US., but here's the rundown:
SEED:
Strike Gundam which is retired for the Freedom by Kira Yamato (main character)
secondary good guys include the Justice and the Buster which change sides towards the third arch of the series
but the "ultimate Good" is the Freedom
Destiny:
Freedom remains the ultra good suit, but the series starts with the impression that the Impulse Gundam is supposed to take off where the Strike started, but its retired from the good guy role when the story flipflops back in Freedom's favor. Also when the Impulse destroys the Freedom, that kills both of their roles as the 'good guy'.
The Destiny then takes what the Impulse starts and its given a 'God Finger' kind of weapon in its palm that pretty much backfires whenever Shin tried using it against the main characters. Also theres the Legend which is a suped up version of the Providence from Seed.
The Strike Freedom then takes over as the main unstoppable goodguy, who is helped out by the Infinite Justice (sadly the writers for Destiny didn't put enough time with that one)
Destiny also has the Akatsuki, which is like the Hyaku Shiki as far as paint job goes but its armor is specifically designed to absorb and repel beam energy making it nearly invincible against Seed's overpopulated beam weaponry.
Astray:
The Gundam Astray units Red Frame and Blue Frame. There's not much super about them as there is their predecessors, but they do stack up with being nearly unbeatable. Red Frame's pilot has an unstoppable spirit of being the ultra-cool good guy and Blue Frame has the war hardened bad ass pilot. Both suits have seen upgrades; Red Frame's OS is given a more melee setting because it carries a katana instead of using its beam weapons, and also adapted add on's such as the Power Loader or the 'Powered' arms which are designed for heavy industry and also for weilding a 150 meter long Katana.
Blue Frame has a wide assortment of heavy weaponry. the Blue Frame 'Second' has specialized weapon units, 'L' type for a heavy melee sword/gatling gun thruster pack, and type 'G' is outfitted with additional armor and cannons.
StarGazer:
The Strike Noir has the combined elements of the Strike Gundam's previous artillery but is the darker character of the serial, not the 'good guy' like the old Strike, but it was unstoppable for the most part of the serial until its final episode with the Stargazer and its energy manipulation system.
but while I'm here, I've got some more background on some of these MS and more in my model reviews at CDX. check em out:
http://collectiondx.com/node/988http://collectiondx.com/node/1005http://collectiondx.com/node/1115http://collectiondx.com/node/1206http://collectiondx.com/node/1262http://collectiondx.com/node/1271http://collectiondx.com/node/274http://collectiondx.com/node/563