NOt as good as Morrowind, but still awesome.
This is an amazing game by any means. It's filled with gorgeous environments, great stories, amazing missions and likeable characters. While the Knights of the Nine add-on is generally just annoying, it does add play value and some pretty awesome armor. Shivering Isles is pretty sweet though. The hilariously twisted Sheogorath definitely makes your decent into craziness very entertaining. The lengthy quest is a nice addition to the already huge game of Oblivion.
The main story and guild quests are all very fun to play through. You generally don't have anything unrelated to do for your quests. And there's a rather funny quest that anyone whose done the Fighter's Guild in Morrowind will appreciate. While there's tons to see and do this game fails to immerse like the 3rd installment did though. It will keep you busy and you will enjoy the time spent, but I got the feeling that very little thought went into the actual layout of the land. Ancient ruins lie mere feet away from big towns, yet remain unexplored for some reason. Caves, mines, ruins and forts seem to haphazardly pop up on your compass as though just tossed onto the map like dice.
The map would be the biggest problem I have in this game. As previously stated the placement of dang near everything makes no sense. It doesn't seem at all well thought out and that really takes away from the joy of exploration. Then there's the overforgiving marker system. Just follow the arrow till you get to where your quest tells you to go. That's it. Whew don't I feel accomplished having followed that arrow? La de da! It really makes me feel ripped off that that big mission I've been working up to took me 1 minute to find and all I had to do was go in a straight line to get there. Then there's the fast-travel system. I can magically teleport to any town or any landmark I've been to instantly. Sure it's a timesaver, but where's the cleverness of the mark and recall spells from Morrowind? Or the Stilt riders. Not to mention there's no levitate spell. All in all it just seems like a simplified formula to appeal to more casual gamers, which is a smart move I suppose, but it makes for a less enjoyable game to me.
I'd still recommend this game to any rpg fan, but for my money I'd say play Morrowind 1st. If you have no intention of going last gen though, you should definitely play Oblivion.