To quote a friend of mine, "If it doesn't have Zeon, it sucks." Once the Zeon arc ended, the Gundam series took a fall. The Zeon made interesting antagonists, since they weren't your cardboard bad guys. From Mobile Suit Gundam to Stardust Memories, you can tell the writers wanted viewers to sympathize with Zeon, just as they wanted to show that the E.F.S.F wasn't perfect, either. During the Zeon arc, the plots weren't just focused on the conflict with the opposing faction, but also dealt with internal strife.
Gundam 00? Not so much...