The Elder Scrolls IV: Oblivion, Is my vote.
If you love RPG's, This is a game you need to own. With this game you really don't need another game for a good 6 months. The amount of content in this game is magical(
). You have your main quest, Which is shutting the gates of Oblivion to thwart Mearunes Dagon from entering the realm of Tamirel, And taking it for his own. The first thing you have to do in this game is create a character, And fuck me its VERY expansive, There are around 30 skills you can master, But they are sectioned into major skills, And minor skills. Major skills are the things that will define you character. You wana be a swordsman? You better pick up the blade, Block, Heavy armour, And armourer(fixing things), Because you will suck if you don't. You can use daggers, Short swords, Long swords, Claymore(two handed), Avakari's(samauri), Mace's, Club's, hammers, many, Many kinds of bow's, Accompanied by a huge selection of bows. That's just the psyical weapons.
Shit that's without all of the magic stuff you can do, Make potions, Fire all kinds of elemental attacks, Make spells, Alter reality, SUMMON creatures that will fight for you, And this is where it gets interesting, I've spent around 4 days trying to become a master of one of the magic disiplines, And its highly rewarding.
I've already touched on the story a little, But i'll go into it a little futher. You are in prison, And the empourer approaches your cell, Due to his family being assasinated one by one, And he's the only one left. His guards open up a secret passage in your cell, And then tell you "You follow us, you die" Then the man in danger speaks to you, And pretty much tells you your the lands savior. Anyway you have to escape through the prison, And you end up meeting back up with those who threatened you, And the empourer get's killed. You are given the Amulet of king's and are told to find his bastard child so he can put a stop to the chaos. So you have to do quest for the bastards child, To get him certain items to defeat Dagon, Which lands you up in a different world at one point.
Other things to note about this game are, You can play in either 1st person, OR 3rd person. The graphics are sublime, The map is expansive, The only time the game has to load is when you enter cities, And buildings.
Only bad thing i've found is that you can get side tracked VERY easily, But as long as you can develop quest tunnel vision, You will enjoy this game immensly.