Easily the best Gundam ending. About all I can say to it. To compare it others, I think the Seed, Wing, Original, 00, etc. All have a similar tone to their endings. Hero saves the day, bad guy defeated, sacrifice made by a sub character. Zeta jumped the ship and decided to just axe the cast other than to have a downer ending.
This is the first one where I felt like it worked for the series' strengths. It's happy, but sad. All the characters that can survive do so and each has a certain future based upon their actions, both good and bad. This is how it works. Alongside Rustal surviving, I think was a great touch. I expected the cartoon ending, but him surviving and living on works well. He's the most popular figure in Gallahorn since 300 years ago. He can re-position himself and them. He's now looked upon as a savior rather than a dictator. It's basically a redux version of 00 S1 ending, which was one of the few good endings in Gundam.