While Dirge of Cerberus strays from it's RPG roots it still makes a reasonably fun, if short, game.
Dirge of Cerberus takes place three years after the events of Final Fantasy VII and one year after the events of Advent Children. It focuses on the character of Vincent Valentine who was a not so secret character in FF VII and was also one of the more interesting and mysterious characters. The story for Dirge involves a secret military division of Shinra called Deepground. Since the story would be most peoples reason for playing Dirge of Cerberus I won't spoil anything but suffice it to say that Deepground has bad things planned, things get epic, the rest of the FF VII cast makes an appearance, and the world gets saved in the end. All while fleshing out Vincent's background and character along the way. The one obvious flaw it has it in the way it assumes you've played FF VII as it gives no real explanation about who people are or anything about the world. If the words Shinra, Hojo, Mako, materia, or lifestream don't mean anything to you then your probably going to be very lost. Aside from that the plot is good enough, but it feels more like a side story rather then a continuation of the main FF VII storyline. It has the distinction of being the only game in the compilation of FF VII where Septheroth doesn't make an actual appearance. It's also over much too quickly as it shouldn't take most players much more then ten hours to finish the main story mode.
Being based on a game that many have called "one of the greatest RPGs of all time" one would expect Dirge of Cerberus to be an RPG as well. But instead Dirge is a third person shooter with some action RPG elements thrown in for good measure. Fans of console shooters should feel at home with the control scheme in short order, but for the rest of us it does take a bit of getting used to. It's worth noting that for us pc shooter fans Dirge of Cerberus does support a mouse/keyboard control scheme which is a nice feature if you simply can't stand the dualshock control scheme. The game itself is divided into individual chapters with no overworld map to speak of. The stages themselves are extremely linear and your never wondering where to go as you basically fight your way from point A to point B in each area. Each level features a handful of bonus missions which are things like save people before the enemy kills them, get to point B as fast as you can, or protect somebody while they do something. At the end of each level you'll be pitted against a boss of some sort and the plot gets advanced accordingly. Interestingly enough, at the end of each level you are ranked on your performance and given experience points that can be used to either improve Vincent's stats or be converted into cash for upgrading your weapons.
You eventually get access to three different types of guns, a handgun (which you start off with), a machine gun, and a rifle. All three of these can be extensively customized and upgraded with money you'll make at the end of every mission and find during them. You can also attach one of three different kinds of materia to your weapons giving you the ability to cast fire, ice, or lightning spells. Sadly your MP never increases as Vincent levels up and he's unable to cast more then a few spells before running out. You can recharge your MP at mako points scattered about the levels or with items you can find or purchase. Alongside weapons, melee, and magic attacks you can also use an item called a limit breaker to transform in a vastly overpowered beast form. The limit break transformation is temporary but you can use it to take down most of the bosses or easily clear out a room full of enemies. Neither the magic or limit breaks are necessary for the most part and you could easily get through the game simply using and upgrading your three guns. In fact you can sail through the game if you simply spend all your money upgrading the base handgun.
Generally speaking Dirge is a very easy game as the most challenging enemy is usually the camera when your in close quarters. Once you finish the main game you unlock a series of bonus missions that should take players longer to complete then the core game. If your wanting to play Dirge to unlock all the bonus features you'll have to scour each level for hidden capsules that you have to destroy to unlock things. These capsules can be found in both the main story levels and in the bonus missions. The bonus missions are much more challenging then the core game; but without a story one would only play them if they wanted to get more life out of Dirge and/or the really enjoyed it's gameplay.
Visually speaking Dirge of Cerberus is a great looking PS2 game. Vincent looks great as do the rest of the characters. The environments can look rather bland at points but given that your running through places like sewers, military complexes, a burnt out Midgar train station, and outdoor canyons it makes sense. One does not expect every room and tunnel of a sewer to look spectacular or different from the last. The same can be said of the enemies. There isn't a great variety of them to kill but it all makes sense within the story, after all, military uniforms tend to look the same. At a few points in the game you'll be treated the the usual CG movie scenes which look as fantastic as one would expect them to in a Square game.
The same can be said about the sound in Dirge, it's pretty much excellent all the way through. All the cut scenes and general voice acting are done well for the most part. Yuffie suffers from a bit of over acting or poor dialogue and there are a few spots of uninspired acting but the most of the characters get it right. The musical score doesn't feature anything that you'll be humming later on, but it certainly isn't annoying either. Towards the end you'll come face to face with a Japanese rock song by Gackt which feels very much out of place but isn't particularly offensive.
If your fond of FF VII, are in need of some fan service, or find Vincent absolutely dreamy you should check Dirge out. If your not that fond of the FF VII universe and/or really can't stand console shooters you'll want to pass it up for a real RPG or a real shooter. While the main story is very short it is also rather good and if your wanting more to do after the bonus missions are enough to keep you going for another five to ten hours. Just don't expect to be playing it for weeks or months like most games that have Final Fantasy in the title.