I pretty much love the whole series, I think BoF1 is my least favorite as well, not because it was bad but simply because it's a very simple and basic game compared to the more ambitious sequels. Overall, I think BoFIII is my absolute favorite, followed by BoFV and then BoFIV. I think this is because III, to me at least, feels like the most balanced games in terms of gameplay, world design, story, and characters whereas the others had a few nagging issues for me. I also simply love how it changed the way you viewed the first two games.

My favorite Ryu is the one from III, followed by his fifth incarnation. I feel like his story and the way he interacts with the world and you watch him grow up made him feel the most complete. Like Rez09 (and most of the BoF community it seems) I feel Nina's BoFII incarnation is easily her best incarnation in terms of story and character development.

Favorite OST, a toss up between BoFIV's awesome Asian influenced music or Hitoshi Sakimoto going back to his MegaTen roots to compose Dragon Quarters oppressive soundtrack.

In terms of story, I think Dragon Quarter might actually be my favorite but I go back and forth between it and BoFIII. I lost dystopian futures and I felt BoFV did a great job of creating one of the most craptastic worlds in a video game with several twists and turns as you uncover more of the story and learn more about the characters. The very theme of racing to the fabled surface before the characters died really translated well into both the story and gameplay. On the other hand III really has a nice twist of taking a story that initially feels like something out of the 16-bit era and then twisting and changing it around to show you that not everything is as black and white as it was before. Myria/Tyr was a plot device turned last minute final boss in BoF1 but III transformed her into a more complex and sympathetic character while also changing the way we really viewed the Dragon Clan. Watching Ryu grow from his troubled but still black and white morality to the morally ambiguous adulthood where he really begins to question Myria and the Brood's goals was a real nice change of pace after dealing with evil demon summoning cults in II and card carrying evil Dark Dragons of the first game. It also helps that III has my overall favorite cast of characters.

In terms of favorite characters I really love Katt from BoFII. I love Rei, Teepo, Momo, and Garr from III; and Fou-Lu, Scias, Ershin, and Ursala from IV. I also loved Zeno Bosch, Elyon, and Vexacion from Dragon Quarter. Honestly this series has too many cool characters. Not to mention mother smurfing Dias/Bleu from the first four games.