Open-ended taken to another level
Oblivion carries a impressive rich lore that can be learned through the various book scattered all over the cities; it is presented also by the townsfolk, through quests and simple chats. It's noteworthy how everything in the Elder Scrolls' universe is connected to the lore somehow. Each race have their own background that justify theirs unique skills and feats. In-game religion plays a crucial role in how to approach missions, as you can deal favors for the Daedra in exchange of powerful magical items or be blessed with stats boosts by each one of the Nine gods.
As a RPG, Oblivion displays a not usual scheme for skills and leveling up: killing monsters won't give you XP, instead, you have to build your skills (you can do that by killing monsters too!), and doing so for your major skills, you will gain a level and can improve your stats. These works in various ways, both traditional and not. For example, strength will alter you encumbrance, but will not (at least directly) alter your damage with melee weapons.
The open-ended nature of the game delivers a huge world of possibilities, that can be so mind-bogglingly that it can prevent you to finish the main storyline (It sure did it to me). Interesting enough, the side-quests are not repetitive and can provide you valuable gear for future adventures. Some people will give you good-aligned quests as your Fame ramps up, or dirty jobs as you become an infamous villain.
The gameplay is simple and efficient, using both mouse (for combat and interaction) and keyboard (for quick access slots, shortcuts and casting spells). The 1st person melee combat is exciting, but sometime you'd wish to see your character in action. Not to worry because you can be 3rd Person slasher, but this view mode loses some precision.
Graphically the world of Cyrodiil is gorgeous and very detailed. The regions are well defined (as the Northerns ones, in Bruma's surroundings, are icy and high, and the eastern are shore based warm). Each region have it's own vegetation, predominant race, architecture style and even social stats as general wealth or demographics. The game runs pretty well and is gorgeous even in more modest settings. But when in highest quality mode, the world really comes alive, the views are breath-taking and the level of detail and care that the developers had is clearly visible. In a game so immersive, the physics are pretty out of place. The player can jump heights greater than his/her own. The objects in game tends to act normally, but corpses assumes a Rag Doll model that is either funny and disturbing. Try to launch any dead enemy from a cliff and see what happens.
In the end, Oblivion is a beautiful and carefully designed RPG that is bundled with a impressive detailed and rich open world to you explore and interact as you want.