In Gundam WING, they were supposed to be 'Invinisible Mobile Suits'. I remmeber them saying Gundams are mobile suits made out of Gundamium or something, and indestructable metal.
And the Gundams never were damage, never defeated unless they fought another Gundam. Nothing could touch the Wing Gundam, the Deathsythe lived forever, and just when you think that the gundams are going to be vulnerable, things like Wing Zero, Deathsythe Hell, and other suits like that show up. Not to mention the most important part of the series, the characters were incredibly boring, without any personality for the most part.
In SEED, I prefered the first part of the series, because Gundams weren't invinisible. Kira in the Strike was given good fights from just GINNs and BuCUEs. Once he got the Freedom, yeah, that was when it seemed like the Invinisible Mobile Suit, and only really had problems with other Gundams. And if Destiny showed us anything with the destruction of the Freedom, by an inferior mobile suit, they aren't invinisible mobile suits in that.
As far as I'm conserned, ALL Giant Robot animes rehash animation. They did it in Original Gundam, they do it in Robotech, they did it Gundam SEED, Wing, all of them. However, when grading animation, you have to look at the quality of animation. The animation in SEED and SEED Destiny were alot better than that in Wing, simply because its a new show.