Oblivion is the ultimate nerd's game. Simply because you will have to have so much spare time to play it!
I'll start with the story - you are a prisoner rotting in a jail inside the huge imperial city of Cyrodil. While being taunted by a fellow prisoner, the emperor and his agents (the blades) suddenly come into your cell and the emperor seems to recognise you from his dreams. It turns out the emperor is escaping from the city because of assassination attempts and there just so happens to be a secret passage out the city through your cell. Co-incidence???
Anyway, you escape from the prison and embark on a quest for the emperor to find his long lost heir.
The story is nothing short of breathtaking. It's not only very long but it's extremely engaging and acts as a good incentive to want to play the game. Some of the story missions are superb in the way that they draw you in. At one point you have to infiltrate a secretive cult and as you go further into the maze of tunnels following your fellow cult-members you feel almost repelled and desperate to get out before it's too late.
The graphics are excellent and I would be lying if I said you don't need a very powerful computer to play this on. But you could almost justify the purchase of a new computer just to play this game - yes, it really is that good.
My only quarrel from the graphics standpoint is that from afar - say, if you in a huge valley looking across to the other side - the textures are hideous and can spoil the game. You can remedy this however by downloading mods - gamespot have all the best one in one downloadable pack - however the instructions are not always clear so it depends how much the bad textures bother you. But be warned they are awful.
Sound-wise the game is great with some fine music and excellent voice acting - including a performance from Sean Bean.
The gameplay is simple but effective. You can choose from a 1st person or 3rd person perspective, though I'd highly recommend 1st person. The action is fast and fun and doesn't get too bogged down in complex manoeuvres. The game is mostly role-playing but there are plenty of fighting sequences and the game certainly doesn't let itself down on this front.
I mentioned before that the game world is huge, and it is, but you can auto-travel to anywhere you've already visited which is an excellent addition to the series. The real bulk of the game comes from the side missions. There are a good few factions to join, each having a wealth of quests for you to embark on, plus most of the people you meet on the street or in the pub have something for you to do.
This game is massive. There are tonnes of things to do, places to go, items to collect and spells to learn. This review is already about twice as long as I was hoping to write and I still haven't covered half of the things you can do in this game. But that is a good thing, as finding these out for yourself will be a rewarding experience in itself. If you own a 360 or good PC, it would be a crime to miss out on it.