Nope. I don't think so. I love Fallout 3 and hate Oblivion. Fallout 3 really fixes a lot of Oblivion's problems and builds on it. Plus it's so much more fun and interesting. I thought I'd love Oblivion, but I've never been able to get all that into it. It's not a terrible game or anything, and I've had some fun with it, but it seems very repetitive and kinda boring to me. There's also so much more diversity in the world of Fallout 3. In Oblivion, so many places seemed so similar to me that it could be hard to tell if I was revisiting a place I've already been to. Also, the guards are unbelievably annoying and I never found the characters in Oblivion to be interesting.

If the fantasy setting is your things then you will probably end up liking Oblivion.  The main difference obviously is no guns or post apocalypse, but there is still a great emphasize on the game world and the sheer scale of Oblivion's world is much larger than Fallout 3's.  Oblivion should be pretty cheap by now so even if you don't like it, it's not like your spending $60 on it.

It depends, as long as you like a fantasy setting and can deal with first person hack-n-slashery then I'd say go for it. The world feels much more populated and gives the impression of a quest around every corner, which can lead to aimles wandering. Not that that's necessarily a bad thing. Still looks as good as ever (the peoples faces were just as ugly then).

The most annoying thing about Fallout 3 as a Bethesda fanboy is that treasure hunting is pointless the unique weapons dont have different models.
I spend almost all my time playing these games dungeon crawling for unique and cool looking items..Fallout sucks in that department.
Oblivion's main quest is awful though it get really repetitive about 2/3 of the way through.
Apart from that Oblivion is bigger and better than Fallout 3 As is has so many awesome side quests.

Maybe. There are plenty of people on these forums who hate Oblivion and love Fallout 3. I personally like Oblivion more, for it's more open-ended nature and bigger size, but you should at least try it out.

Aesthetically, they have a lot of the same features:  first-person RPG gameplay, tons of skills and items, massive world.  However, in Fallout 3, you level up by gaining XP.  In Oblivion, you level up by increasing certain skills that you set as your primaries during your character creation.  Essentially, you can hit max level by simply choosing Athletics and putting a rubber band on your stick to keep you swimming in a corner, then check back every once in a while to make sure your controller hasn't disconnected.  It's stupid as shit.  Also, there's no guns...or VATS...or post-apocalyptic wasteland...or Harold. 
 
Personally, I hate Oblivion, but a lot of people seem to disagree with me.  So whatever.  It's so cheap that you should pick up the GOTY Edition of it just to whore the 1250 achievement points.  After that, if you still like it, then cool.  If not, well...you got 1250 easy but time-consuming achievement points.

  I am living this right now. I LOVED Fallout 3 and having never played Oblivion, upon completion of Fallout, I picked this up. I don't know if I am just suffering from Bethesda fatigue or what, but I cannot get into this game at all. Truthfully, I think it's the story. Fallout 3 started with a really clever way of getting things going by having you go through your young life in the vault, where Oblivion really just threw you into a story in a silly way (who would put a secret passage in a jail cell?). Also, one of my favorite moments in Fallout was first leaving the vault and entering this totally fucked world. When I started Oblivion, I expected something similar after leaving the sewers. Nope. Beyond this, I think my biggest problem getting into Oblivion is that the world in Fallout is far more interesting to me. I like fantasy-type games and movies, but the Oblivion world is just sooooo boring and generic to me. I'm still going to try and play through the whole game, I just wonder if I had played Oblivion first if I would feel the same...    

It's too difficult to say...typically people enjoy one more than the other...I strongly disliked Fallout 3 and loved Oblivion for example.

If oblivion had VATS it would be awesome. nothing beats running backwards firing fireballs and watch them fly by a goblins head. I hated Oblivion but loved Fallout.

I suspect you will enjoy Oblivion more.

Well I loved Oblivion I think you should if you enjoyed Fallout.

I loved Fallout 3 and disliked Oblivion... but thats just my opinion...

would you like fallout if was in a much better looking world, and had a ton more things to do in it? if yes then you like it

Fallout 3 was alright, but Oblivion is easily my favorite singleplayer game of all time. If what you liked was the post-apocalyptic setting, then Oblivion might not be for you. But, if what you liked was the epic sense of scale and the large gameworld, you'll probably like it.
 
Personally, I think Oblivion's world is much nicer (fantasy, everything's not dead and brown), and it feels much more populated with both NPCs and places to explore. Plus, unlike Fallout, the various guilds give you tons of fun quests to do. If you do pick it up, I'd suggest forgoing the goody-two-shoes route. The Thieves Guild and Dark Brotherhood are too much fun to miss out on. Also, Shivering Isles is a must, the other DLC not so much (I think GOTY edition comes with SI and Knights of the Nine). 
 
I've put 150+ hours into the game, playing through it three times: Once as a "good guy"  brawler doing pretty much just the main quest and some side stuff, once as a magic user doing all of the guilds and the arena, and a third time playing as an archer doing just Shivering Isles.
 
Obviously, I can't recommend it enough.
 
EDIT: Well, after seeing this was started a month ago I looked at your achievements and see you've already beat it. Still, what I said stands. Check out the other guilds and SI if you're still into the game.