I felt the best final fantasy ending was FFX. FFVI through to FFVIII were better games but the excellent voice acting and advancements in CG technology utilized in FFX immersed me so much, it was like watching the end of a really good film.
I wouldnt go as far as calling it excellent, good maybe but far from excellent. It was a massive accomplishment and a step forward for having voice acting for most of the game (and a LONG game at that) I will agree with you on that, but the qaulity of some of the voice acting talent was attrotious.
Tidus - God the numerous amount of times I just wanted to rip his vocal cords out...
Yuna - Another annoying one because her voice was constantly high, low, high, low (especially during the emmotional parts of the story)
Rikku - Same as Tidus but 10x worse
Wakka - Not really the sound of his voice but the accent really annoyed me
FFXII on the other hand had some of the best sounding voice actors I had ever heard in a game, Fran and Balthier especially, but it was let down by the mediocre story and lack of character interaction. Another thing that spoiled it for me was that they were boasting about having a huge ammount of different races in the game, more so then any other Final Fantasy to date, yet we only got to play as 1 Viera and 5 Humes
One thing I hope they do in the future since Blu-ray can hold more data is include the Japanese voices as well with the option to turn on English subtitles (its already happened with Blue Dragon and Naruto on 360) since thats the only thing I dislike about JRPG's is that they usually force the English voices upon you, which in most cases suck.