Oblivion has a lot of content and a strong action aspect, but the roleplaying falls short.
The dungeon you begin in acts as a tutorial as well as an extended character creation process. The controls are simple and intuitive enough that by the time you leave the starting dungeon you should be comfortable with all but the most advanced techniques of controlling your character and using the interface. If you're an avid PC gamer, you'll quickly notice that the interface is not streamlined for the PC. The icons are huge and plenty of scrolling is required to find what you need. The inventory quickly becomes cluttered with junk that you don't need to know is there, like keys and scrolls and you have to scroll past them every time. Transferring mass amounts of items in or out of crates is also much more time consuming than it should be. There are mods now available that alleviate inventory gripes to some degree (although I personally didn't find one quite to my taste), but that is no excuse to not properly develop an interface for the PC.
Other interface features include a compass, your standard stat meters and information on your current spell and weapon. The compass combined with the hold your hand style of the quest logs (that pop up on your screen everytime they update) makes Oblivion ridiculously easy. Gone are the days of finding people and entrances, along with the satisfaction of actually locating them. Even locations of interest that you're a fair distance away from show up on the compass. It should be noted that I added mods that decreased the auto-show distance to about five metres and removed the quest pop ups. The personal status interface items do their job, but the quest log and compass take a lot of the challenge out of the game. Character creation is one of Oblivion's strongest points. You can choose from any combination of race, birth sign and major skills. Just about any form of mage, thief, fighter or smooth talker conveivable is possible to create. Not all of the styles are equally supported throughout the quests in the game, but there is at least a questline for any character.
Combat as any fighter style initially feels good. However, by the end of each dungeon where there are many enemies with similar combat styles, fighting can be a chore. Fights often feel drawn out as most enemies have large amounts of health or can heal themselves. So once you find the pattern to damaging the enemy, it's just a matter of repeating it as you wittle the enemy's health down.
There are other minor gameplay gripes, like silly mini-games, enemy levelling and 'all-or-nothing' perks from skills, but I won't go into detail about those.
The world of Nirn looks pretty thanks to some spectacular graphics. The exterior is well crafted and you can see quite the distance. Unfortunatley frame rate hitches aren't uncommon in certain areas and this causes outdoor fights to sometimes be frustrating as you try and line up spells. On the other hand, interiors run without a hitch. This is to be suspected though, as the dungeons appear bland and don't have much in the way of detail. The other form of interiors, buildings, run smoothly, and are detailed with decorations. People, weapons, items and just about every form of object look great. Everythign looks fantastic and the artists did a more than adequate job of using the engine to make the world stylish.
The general audio throughout the world is decent. It does enough to convey the sound you would expect, but does nothing to truly stimulate your ears. You hear rain and you know it's raining, but it doesn't convey a rainstorm. You hear a punch and it sounds like a punch, but it doesn't sound gritty or painful. The real highlight of the sounds is the impressive amount of recorded dialogue by the NPCs in the game. While all the race and gender combinations have the same actor, the sheer amount of talking is astounding. Hearing, rather than the usual reading of dialogue makes an amazing difference in how you experience interaction. The general audio does its job, but the voice acting, despite its flaws, is the real shiner.
Whle Oblivion does have a lot of things to do, there is not as much as there initially appears. Most of the dungeons are fairly similar and once you have seen the different art styles of dungeons, there is little point in exploring the rest of the dungeons. The occasional cave or ruin will be unique, but it is a very rare occurence and usually only for the end of a major questline. There are a handful of guilds to join, along with their corresponding questline to take up. Other than the entry level quests, all of the tasks for a guild will be around that questline. This makes your rising through the guild feel rather undeserving as you can go from the second lowest rank to the top by just helping out with one overall problem. The quests in general, do vary, and with a few exception aren't boring. However for an open ended role playing game, the quests have very linear progression and leave little for the imagination or for moral options. Even if you do think up another possibility of solving the problem, you will likely have to solve it one of the ways the quest log informs you to. Quests also have the same outcome, no matter which of the options you take to do it, and it's usually a happy fairy land kind of ending. In fact, you don't even have the option of failing the quest, merely ignoring it is the closest to failure. While the quests are varied, the linear 'accept quest', 'do quest', and 'collect reward' structure leaves something to be desired.
Overall, Oblivion is a solid, beautiful and generally entertaining game. As a playground it shines, but as a universe for role-playing it falls short.