I bought the Game of the Year Edition last year for PS3 and I am a huge RPG fan since the SNES. After all that great reviews I expected an excellent game....... It was shocking how boring the whole game turned out to be in the end.
The main quest lacked in depth. The whole time I was wondering why the character is participating in that main quest anyway. I could not connect to the story/world/anything in that game. In 40 hours that whole game was not fun after the first 20 minutes. I was hoping that it would get better with the story progress... even the quild quests were not satisfying for me. There really is so much content.... but there was not much content for me to enjoy. It was just "more of the same" boring stuff. After 40 hours I gave up on the game.
Oblivion was easily the most boring RPG I ever played so far. That does not mean that it is a bad game... its just not a "thrilling" game for everyone. Since you did not like Fallout there is a really big chance that you will not like Oblivion as well.