One of the most complete games you will ever play, ever. Period.
If you answered yes to any or all of the above then Elder Scrolls IV is frankly the best use of your hard earned(/borrowed/begged for) money that you can get on a PC.
From the moment you start the game, choose your race and choose one of the many professions, each with their own primary skills, or even if you choose to create your own profession with different skills to any of the vast array of pre designed ones, the game's scope becomes apparent.
Complete ability to customize your character, and so many options to choose from, allied with the bonuses bestowed upon your character by his/her birth sign, makes this one of the most complete character creation processes you will ever see.
That's all well and good, but what does that level of customization actually mean? Well 1st up it means you feel a degree of satisfaction in your creation, it is exactly how YOU want to be, and that enables you to connect to the game in a way not often seen. Also it adds an almost infinite set of challenges if/when you choose to replay the game.
Add to that the story which grips you from the moment the Emperor bursts into your cell at the start (it's not much of a spoiler, honest), and you have a hugely immersive and replayable game.
Ok so what of the depth, you can spend an hour or 2 creating an avatar but what good does that do if the gamepay sucks? As soon as you are through the intro sewers and out into the big bad world you have the greatest of things....choice.
Not just the good/bad guy choice, REAL choice of what to do. Do you think it's best to let the nation stew for a bit while you become a master assassin? How about the sound of Arch-Mage in from of your name? Sound good? Thought so. You can choose to do all the quests at your own pace, and in your own style, be that ranged magic, in your face melee, stealthy killing or any combo of the above.
And the game is smart too, contract vampirism and you can't stay out in the sun light for example. The guards will come running if they hear trouble, but have no godly powers to known what happened if they didn't see it. The whole world feels alive from the moment you stop to look around, to when you explore to the back end of any of the small towns and meet a poor homeless person.
Allied to that is a very definitive style, in terms of architecture, geography, dress sense and wildlife/beasts. You really can feel like you are part of the world in which you fight, and the world will reward you for looking around accordingly.
I won't go on any more as it would take from the time you could be playing the game, and you really SHOULD be playing it. There's no reason not to!