It's open world, but there's no driving around.  So it's like Animal Crossing open world(not the same gameplay though,) Shenmue, or games similar to that.  Sleeping Dogs combat is more like Batman Arkham series, where Yakuza's is more of a Streets of Rage, Final Fight type combat system, but in 3D and with additional additional gameplay mechanics like the finisher combos, heat action system, evade, counter system, etc.

There's a lot to the games combat system with the heat system and everything, but as you learn more as you level up, it would take awhile explaining everything you can do.

I need to play this series sometime.  I always intended to play Yakuza 2 but never got around to playing it.  It seems like a good franchise just was never sure what to think about it since im not really all that familiar with japanese stuff.  Kind of figured a lot of the stuff will just fly over my head.

Its good.  Not really confusing or anything.  People post a lot about the series having a lot of Japanese culture that plays a big part in the g ame and maybe that's what sounds like would go over your head, but like in GTA how you go to comedy clubs or strip clubs were added, this game has hostess bars.  Or when going to the hamburger place in GTA.  This one you go to the hamburger place or multiple other restaurants and you choose what you want to order instead of automatically getting a hamburger. 

I guess I should have explained it in the review, maybe will do in the Yakuza 4 review, but everywhere you eat, or if you go drinking, it tracks what items you've had.  So there's a sort of collectathon type aspect to eat all the food, drink all the drinks, get the best score on all the mini games, etc.