Buy it. Yakuza 3 is awesome; it's like a Clint Eastwood movie experience. It starts off slow, slowly developing the main characters, but it pays off since the game does a great job making you care about the characters. I couldn't put the controller down when I got to the final two chapters. The build-up to the finale was fantastic. There's also a lot of nice diversions. The only downside about Y3 is the graphics; they look horrible.
Yakuza 4 has awesome gameplay with lots of funny side-quests & mini-games, but the story isn't that great imo. I'm currently playing Yakuza Dead Souls, and it sucks ass. The framerate is horrible, and all you do is run and shoot. For a zombie game, it lacks tension and atmosphere.
You know what, just buy Bayonetta. You'll love the Jeanne fights.
