Ok first of all, I'm not trying to bash or put down this series.
Basically, three reasons why I dislike the series:
1. I think G-Gundam was the first alternate universe gundam series, and for me, being a UC fan, I wasnt quite ready for the 'shock'. UC Gundam series are more or less on the 'serious' tone like what kosh said, and its mecha design and combat seemed more 'realistic' to me. G Gundam's mecha are more on the 'Super Robots' genre, focusing on 'hand-to-hand' combat (kungfu style) and 'special finishing moves' such as conjuring energy balls - much like Dragonball characters in mecha form. Totally different from what I expect from a 'typical' Gundam show. This is of coz, my own fault for 'expecting' something which it is not, but it certainly didnt help on first impressions.
2. Many mecha designs are butt-ugly, so much so that some of these designs - I dunno whether I should laugh or feel insulted. Fish-gundam, Mermaid gundam, crab gundam, windmill gundam, skull gundam, boatman gundam - I'm sure you'll find them 'interesting'
. Makes one seriously wonder if they spend any time in such designs at all, or was it a brain-storm session where any design goes? Comparing to supposedly 'much older' designs in Zeta, ZZ, CCA, F91, and its immediate predecessor - V Gundam; tell me if anyone dont feel the design quality had dropped a GREAT deal?
3. The main char, Domon Kasshu, ALWAYS
wins. Period. You will know that the combat ends when he uses the special move 'shining' or 'god' finger. Only exception is when his kungfu teacher, Master Asia, uses a similar move, and the fight will be even. Way too predictable. I prefer a story where the opponents at least have some sort of a chance of winning.
To be fair, the storyline was quite interesting with some plot twists and a surprise ending.
BTW, to answer your question on what 'happened', I quote from MAHQ:
"Bandai celebrated Gundam's 15th anniversary by trying something new: free the franchise from the continuity of the the Universal Century (and sell more model kits). "
I wonder if it is considered a successful series? I'd rather have a full series of F91....