these games are completly different and considering the tech differences graphic and game overall this isnt a fair.. ehm how to say, comparement? xD anyhow if i had to choose it is fallout 3 just since i love post apocalyptic games, however if there would be an TES:V i would be all over it in seconds. I do love the fact that Oblivion is acually a more open world with more side quests than Fallout 3, however i like that oblivion is more an RPG aswell, i mean Oblivion is, purely, an RPG, top to bottom. Fallout 3 feels like an FPS with unnecessary RPG elements, it doesnt feel RPG to me, just because you can kill everyone, gain levels and gain skills it doesnt mean it has to be an pure RPG, no, if you are to make an RPG attleast make the character you play a bit more interesting, make the storyline around you more interesting, make everything RPGish, Fallout 3 didnt have this "rpg atmosphere" like Oblivion had. In fallout 3 i felt like i was more or less like a merc on a special mission to do bla bla, I didnt feel special although i was special. In oblivion you feel special, everyone looks up to you in the end, some people might aswell hate you, Oblivion is an ultimate RPG experience while Fallout 3 is more like a... shooter with some RPG inputs.
Now i better start complaining, Fallout 3 is an absolutly lovely game and i simply love it, for what it is, not for the "Rpg" feelings, which simply imo doesnt exist, no i love it because of the world, i love it for the VATS (right?) system, i love it because you can kill EVERYONE (except main characters), i love it for the gore, i love it for the creatures, i love it because of that mission in a vault when you go back in a black and white world(fav mission in all the game).
How much i even love Oblivion it cant compare to Fallout 3 because fallout 3 has so much more technology behind it so oblivion feels like crap.
Conversations are still crap thou =P

[Q]uik, Quiker than most