G Gundam's in my "currently watching" list at MAL, actually. Borrowed the DVDs for the first half from a friend, and working through the Baka-Anime releases for the second half. I'm no Gundam expert, but afaik G Gundam was one of 3 "Alternate Universe" series commissioned to commemorate the 15th anniversary of Gundam. (First Gundam aired in 1979, so that would put G Gundam (1994) squarely in the historical middle of the Gundam franchise.) According to the DVD extras, it was also very merchandise/toy-driven, thus explaining all the outlandish robot types.
I don't know if it's the "1 exception to the rule," but it is quite different from what we would consider "normal" for Gundam. I understand that many hardcore Gundam fans dislike G Gundam, but my take on it is that it's not a mecha series and only barely a Gundam series. It's a shounen/tournament fighting anime that happens to use giant mecha in the battles. If you think of it that way (instead of expecting it to live up to the Gundam reputation), it becomes an anime like Scryed -- completely "dumb fun," cheesy, over-the-top, hot-blooded action. Not the greatest in the plot or character development departments, but it never fails to entertain.