It depends on what you like about fallout. do you like the fact it has dialogue options, interesting side quests and a non-generic setting? If so you wouldn't like oblivion since the quests are on the boring side, the setting is general lotr clone fare and you can either do a quest or not do it. And there's only one way to do said quest.
However if you like exploration and don't mind much about having a cliched setting and minimal freedom/dialogue options you'll probably love oblivion.







