I saw Yakuza 3 and 4 at Gamestop a few days ago but didn't pick it up because I didn't know much about the series other than what I've been hearing from your blog and a few things here and there on other websites from back in the day. Ended up purchasing White Knight Chronicles 2, which was a bad choice. My question to you is, can a person that's never played a Yakuza game jump in anywhere? Or is all one cohesive story with the same characters?
As far as the Yakuza series goes, a small portion of recurring characters is the biggest cohesion that spans throughout the games that I can remember. I jumped in with Yakuza 3 and aside from the handful of aforementioned characters the game expected the player to know, it doesn’t really slow you down all that much. Yakuzas 3 and on include videos that sum up the entirety of the previous games, likely for those who want a refresher or people like yourself who would be jumping in fresh.
tl;dr yeah (if you like 3 though pick up the rest, 1 might be hard to appreciate after playing the sequels but 2 is supposed to be the high point of the series even with how great 3 and 4 are!)