hi, have played fallout 3 120+hours liked it but got very repetitive battle, stories are good and theres plenty to explore, i would recommend this and now comes with a few expansions but they are quite expensive. oblivion on the other hand i barely started, its absolutly massive, i wouldnt have the time to enjoy it properly but word about says its the best elder scrolls. hope it been helpful and not too late
First and foremost; both similar and are both great games. But less about the similarities (of which there are many) and more about the differences;
Oblivion is a larger game, there is more to do, and there is more to customise in the world. With access to mounts, creation of your own spell and items from the captured souls of your enemies, and so forth. Oblivion's character advancement is much better than Fallout, and it is skill based. As you use skills, those skills get better. The problem that exists in Fallout with the enemies getting harder as you do also exists, and one of my pet hates with Fallout 3 AND Oblivion. This phenomena mean that as you get tougher, if you dont level properly, the game gets harder (relative to your skills). There are amny more NPC's to interact with, and you can even contract Vampirism (from vampires of course) and get the benefits (and penalties) associated with the condition. What does Fallout 3 have over Oblivion? Graphics, and polish. Whilst Fallout 3 is buggy as hell, it pains me to admit it, but Oblivion is worse. Some quests can easily be broken meaning they cant be completed, glitches are common and voice acting is terrible (sometimes with different actors speaking different sentances in a conversation for the same person). If you like RPG's go for Oblivion, if you prefer the casual experience, go for Fallout 3.
Fallout 3 all the way. Oblivion just didnt compel me enough to want to be bothered to play past the 1st couple of hours. Fallout 3 is so much easier to get into and more compelling, and it's different in the sense that its not a typical horse back riding/sword fighting RPG, if you get my drift. The atmosphere and characters in Fallout far surpass oblivion, I just didnt care about the story or characters in that game so soon became bored. Fallout 3 is huge with endless freedom but isnt overwhelming when it comes to the game play mechanics. Theres still lots of things you keep coming realising you can do but oblivion tends to throw everything at you without explaining how or why you should being doing most of those things.