Yakuza isn't Shenmue with guns (it's barely Yakuza with guns) and that misconception is potentially its downfall.
The reason I bring up Spikeout is because while Yakuza has been mentioned in the same breath as Shenmue and Grand Theft Auto in the past, both in marketing talk and people hamfistedly describing it in previews, it's not terribly reminicent of either, as a matter of fact. It's essentially Spikeout with a chunk of tokyo wrapped around it and a proper, well written and reasonably well acted story.
Of course it'd be a disservice to leave it at that, because it is certainly an infinitely deeper and more compelling experience than Spikeout was.
A lot of the time you'll be running around in a district of Tokyo (fictional one at that from what I gather) and this is handled in a pseudo Devil May Cry/standard RPG fashion, camera and interaction wise. You'll be able to talk to certain civilians and sometimes get sent on small sub-quests for money and/or experience points. The RPG comparison is especially valid because you'll also encounter semi-random battles, where someone yells something and runs towards you. You can escape these by running away, but more often than not, you'll run into them, triggering the encounter immediately.
When this happens you're transported into a combat scenario. This takes place in a confined place surrounded by either people or walls, based on the area you were attacked in. This is where the game is essentially transformed into an advanced Spikeout. In addition to a growing assortment of moves, you can pick things up in the environment - Stuff like lead pipes, traffic cones, restaurant menus, etc - and whack baddies with them.
Once you've whacked people a sufficient amount your HEAT meter is built up and enables a bunch of powerful context sensitive moves. These also grow in numbers during the course of the game and consist of, for instance, stomping in the face of a grounded enemy or grabbing him by the neck hair and whacking his head against something unpleasant. It all looks deliciously violent, and it's a near orgasmic feeling topping off a big brawl with a couple of subsequent heat moves like that.
So, needless to say, lead character Kazuma Kiryu isn't a very sensitive person when it comes to street scum. However, as a person, he's as kind as they come.
Yakuza's story kicks off when Kazuma takes the fall for a friend's accidental murder of their "Oyabun" which is basically Yakuza talk for "boss". His friend - Nishiki - goes free and Kazuma himself is expelled and sent to prison for 10 years. Once released, he faces not only a world that has little place for him, but also a friend that no longer seems so sympathetic.
Many of the themes seem extremely familiar, and one could probably point fingers and scream cliché, but that's only if you've seen the kind of material this story borrows from. Even if you are a big fan of japanese crime stories and have seen a complete bunch, though, this story still manages to take a few turns you didn't see coming, and do so with what's certainly one of the tougher main characters around.
Cutscenes and fighting are padded well with a free roaming city portion. You can walk anywhere at any time and visit one of many "hostesses", gambling areas, stores and so on. The omission of playable Sega arcade games in the Club Sega places is probably only noticable to those that played Shenmue 1 and 2, but it's still fairly disappointing considering all they have in there is a crane lift machine.
Going to a hostess is actually more fun than it sounds (or is that the other way around?) because it triggers what's essentially a dating sim. It's actually surprisingly satisfying to answer her questions right and drink her under the table. Of course if you play your cards right you'll eventually get to sleep with them, possibly in the most anti-climatic fashion since Larry 1. There are a variety of different girls you can approach, and all of them have their own unique preferences.
There's also gambling to be made (or had?), but at the time of writing this I've spent too little time with it to write anything in depth about it. The story pretty much always has you running around rescuing people and stuff like that, so it's difficult to find a good time to do these things. It's not that any of it has a time limit, but it doesn't quite make narrative sense to go gambling when somebody's house is on fire. I can say, however, that there's a complete bunch of different games you can play, including roulette, dice and cards. Money can be won, experience can be collected.
Experience, yes. For different things in the game you gain experience, and just like any RPG you use them to become stronger. In Yakuza you basically upgrade one of three different gauges. Each one represents different combat aspects, and through here you also gain access to more moves. Later in the game there's also a guy that teaches you moves that you can't acquire through mere grinding.
That's basically all there is to Yakuza, and that's probably also its biggest problem. In these post-Shenmue times when people are still waiting for Sega to deliver either a true sequel or some equivalent, it's easy to take a look at Yakuza and assume that's what's going on there. It isn't. Yakuza is a painfully or refreshingly simple game, depending on how you look at it, and if it's an evolution of something it's the scrolling beat em up genre, not action adventure/F.R.E.E. or whatever they called it.
Yakuza succeeds on most of its endeavours, albeit to varying degrees. The story, while well written and mostly well acted by Lex Luthor, Faith The Vampire Slayer, Mr Blonde, Luke Skywalker and friends, never quite connects the way they obviously hoped for. The emotional scenes are hardly ever moving on anything but an aknowledging "okay, this is supposed to be moving" level, and that's probably the most unfortunate thing about it. It still has awesome characters, a good dose of badassness and perhaps most importantly; both a tone and content that is sophisticated and unmistakably mature. It tackles its themes with almost relentless integrity, and if you don't know what an "Oyabun" is, for instance, the game isn't gonna stop to explain that to you.
Fighting is obviously the bestest thing about Yakuza. It's the base of the game, the thing you'll spend the most time doing (that or trying to get into hostess panties) and it's quite frankly worth the price alone. It might start out somewhat awkward, but later on, as you learn to mix things up and get really good at it, it has moments of true bliss.
In the end it's really a matter of expectations. Do I judge this on the merits of Spikeout gone story driven, or do I see a crime saga that attempts to tell a moving and thrilling tale while borrowing gameplay mechanics from jRPGs and old school beat em ups? Yakuza comes across as a big budget production on account of its star-ridden cast and Takashi Miike directed prequel shorts, but it doesn't really live up to that status. Ultimately, Yakuza is not enough of the game you want it to be - partly because that was never the intention - but it's plenty the game you discover when you play it, and that's certainly good enough.