Oblivion is an incredibly ambitious game, but the good news is that it delivers on the vast majority of them.
Cons: Slightly repetitive; minor performance issues; too many loading times; slightly clumsy D-pad hotkeying; lack of feeling of increase in power; feels slightly aimless by nature.
Oblivion is a huge, ambitious, massive RPG that succeeds at accomplishing the majority of its goals extremely well. It's in all probability the best game out for the XBOX 360 and worthy of anyone's purchase.
Oblivion is, of course, a single-player only RPG (somewhat of a dying breed these days) that finally succeeds on a lot of the previous ambitions that the Elder Scrolls series has always had. It's a huge, believable fantasy world (other than a few quirks), it looks and sounds amazing, it has a delirious number of quests and things to do, as well as an incredible amount of variety. After going through the character creation - which has a dizzying amount of variety in it inherently - you start off in the slightly cliched setting of a sewer, after a dramatic cutscene voiced over by the venerable Patrick Stewart. Eventually, the Emperor (Stewart) and a few of his guards just 'happen' to have to escape through a secret exit (having heard wind of an assassination attempt) and the Emperor claims he's seen you in a dream. You follow along, make your way through the sewer, and then, eventually, burst out onto the world.
The sewer dungeon might attract your attention due to the top-notch voice work (everything in this game is voiced), the physics (which are mostly just for effect), and the fast, tight, combat, but in reality, it doesn't show off what Oblivion is really about. It's merely an introduction to the core mechanics - which you can pick up pretty quickly - and then you come out, undoubtedly slightly blinded by the world, to see a huge, huge world, lush and green, and, although you don't know this yet, populated with tons and tons of characters, quests, and stuff to explore. And therein lies the true appeal of Oblivion - though it has an excellent main quest and story that you can follow single-mindedly if you wish, you can just as easily, once you're out of the sewer, completely forget about the main storyline for the rest of your time with Oblivion. The game even encourages you to go out and explore as soon as you make it out, and it is indeed awfully tempting.
One of the requirements of this system is that Bethesda decided to do away with usual RPG conventions, which mean that as you go both you and your enemies increase in power so that if you went back and fought the old enemies, you could crush scores of them with a wave of your hand, and designed a system with a difficulty ramp, where, as you increase in level, so do all of your enemies. This means that you are genuinely free to go anywhere and do anything that you want at any point in the game. However, this is a slightly double-edged sword, since the drawback is that you really don't feel as if you're increasing in power as you progress in the game, which has always been a major part of the appeal for any RPG game.
Another step towards complete open-endedness is the idea of 'fast travel'. In order to do away with unnecessary and boring travel time, Bethesda gives you the option to warp around the map to cities and landmarks. Unlike the difficulty setting, I do not feel that this is a double-edged sword. If you feel that this takes away from the cohesiveness of the game, then simply ignore the feature. I would advise you to use it though. This allowed the designers not to be afraid of spreading out the quests among the entire map since travel time is so effectively reduced; in short, there is no pointless land in this game.
Oblivion's core systems are quite simply and very effective. Like many RPG's, you choose a race and a class - though you can create your own class anyway - and get to work. The three main systems are magic, combat, and stealth, and they all work quite well. Mostly, they're handled through the triggers - for example, for melee, hold the trigger to do a hard hit, do it lightly to do a fast hit, and so on - but what's unique about this game is that there's not such a focus on specialization. It would be very hard to create the kind of pure spellcaster character that is found in other RPG's, or the pure warrior, simply because every character can do anything. Your class and race only give you slight advantages in certain skills - they hardly limit you to just using those skills. The other reason it's so easy to create hybrid characters is because, unlike most RPG's again, you don't increase your proficiency in things by gaining a level and then putting points into certain attributes (though you do level up), you gain proficiency by simply doing the thing. So if you cast healing magic a lot, then you'll become better at restoration magic. This system is quite intuitive, spares you unnecessary number-crunching, allows you a lot of freedom to switch play-style on the fly, and simply makes more sense than the usual system. In fact, the only complaint I had with the core gameplay systems at all was that it was somewhat clumsy to switch between different weapons and different spells using only the d-pad, especially as you increase your number of spells, and this is one aspect of the game that would perhaps work a little better on the PC, where there are more buttons to map out to different spells.
Oblivion is a gorgeous game. The art design, while admittedly familiar in fantasy territory, is quite good, but it's the sheer power of the graphics engine that induces the awe, and on the XBOX 360, it runs and looks better than Oblivion ever will on all but the very high-end PCs. Reflections, physics, grass, trees, they all just look very, very good. Performance-wise, it's not perfect, however, the 360 will occasionally stutter a bit and the framerate might dip, though it mostly runs fine, and worst of all, while the loading times are relatively brief, they are far too frequent. In fact, they might just be the worst thing in this game, since they take away from the otherwise extremely cohesive and seamless world.
The other half of the presentation - the sound - is even better than the graphics. The score is quite good, though once again, somewhat familiar. The most amazing thing is the sheer amount of voice-work gone into this game - every single line is recorded, and voiced quite well, and it adds a lot to the immersion of this game. The sounds of battle, the thuds and grunts and hits and sword-swipes, the magic spells and arrows, all sound superb as well.
Oblivion might feel slightly aimless by nature to some people. Yes, there's a quite lengthy main quest there, but the game is really about everything there is to do inside this world. The amount of detail in this place is simply unprecedented. All in all, Oblivion is a simply superb game that has a plethora of compelling reasons for anybody, whether they're a fan of action games, stealth games, RPG's, or just games in general, to pick it up.