Good question! Favorite Gundam show... I suppose it is reasonable to say they all have their moments. But to get down to just one? I gotta go original and cast my vote for Mobile Suit Gundam. Amuro in the RX-78-2 and Char in his custom Zaku II, Z'Gok, Gelgoog, Zeong...whatever he could get his hands on. Great characters that stayed so till their end. Universal Century I think has the best staying power.
I will admit G Gundam is not a favorite. I would watch another show before that one. X, Turn A, Wing, 00, they all come in way before the Gundam fights for me. Seed I think was great. Destiny let me down, Shin killed that series for me. They had a great opportunity to expand on the characters with the political setting, but it just became one crying episode after the other. I kept rooting for Kira to kill Shin! Then I pulled for Athrun to kill Shin! Then I hoped Cagali would end my misery and kill Shin...you get the point.
Unicorn looks to be impressive. The mechas are outstanding. I look forward to the rest of those!