I watched Turn A and it was amusing watching them 'dig' out Gundams from under the ground but I think I lost interest in the series sometime past the part where the main character dressed up like a girl. I wasn't too keen on the cockpit location either.
Seed S1 and Gundam 00 S1 were both good though I still prefer 00's first season. Both second seasons were pretty bad for me. S2 for Seed and 00 were bad enough to make me appreciate Endless Waltz more and I really didn't like Endless Waltz.
I do like the basic units from Seed (Astray, 105, Cgue) but I'm not a fan of the main units. Duel looks plain and boring, Buster just looks imbalanced in design, didn't fancy the pointy shoes on Aegis, though Blitz was okay. I don't remember anything from Turn A that I'd like to play. As for 00, I definitely want a few of Graham Aker's custom suits.
G Gundam had a more consistent story/plot than 00 S2 and Seed Destiny if you can look past stuff like Gundams hugging rockets and blasting off into space. It's still my favorite because I was mostly into Street Fighter and didn't really pay attention to Gundam until I saw them punching and kicking each other in a tournament. :P