They are both good, they both have a different storyline though and take place on different continents in the world.

Oblivion is incredible. A classic example of a game that gives you a wonderful first experience.

Eh, playing Morrowind with all the incredible PC mods it got made Oblivion feel... lame.  The developers really didn't do anything interesting with it.

The mods for oblivion are quite interesting too. You can even fly dragons.

Morrowind is superior to Oblivion in my opinion.

Both are good games but Oblivion just felt slightly dumbed down in comparison to the glory that was Morrowind.

Of course half the people I know couldnt even play morrowind because its so hard to get into to start with as it doesnt push any quests or anything on you.

Like Rath said Oblivion is more of a dumbed down version of Marrowind.

Of course, it is a gorgeous, huge, and at times hilarious dumbed down version of Marrowind.

Can I put a vote in for Daggerfall(Elder Scrolls 2)? You can get any or all of those Elder Scroll series though. I've enjoyed them all.

Oblivion bored the hell out of me. Basically a prettier version of Morrowind with a lot of freedom taken away. Can't kill main characters now, enchanting and spell making is locked up and only avilable if you rank up in the Mage's guild. Nasty caps on the spells, potions, and enchantments you make. Bah.

Remember how cool finding that unlucky bastard with the super jump scrolls when I started Morrowind. Immedately 
used one and landed in the ocean, and was killed by slaughter fish. Oblivion is just so much more restrictive and 
forbidding. 

If you do get Morrowind, I suggest you get the PC version. I have two anecdotal sources who tell me that it's better than the Xbox release.

PC versions are usually alot better, thanks to mods