This game is awe inspiring...
One thing that I like of Elder Scrolls games is that even though there is a central quest you can follow, you are not "forced" to follow it, which is what happens in most Bioware games. They are great, but forces you to a certain path.
You can join the fighters' guild, the mages' guild, thieves' guild, become an assassin. Each have quests to perform and you will grow in certain skills by completing them.
Graphically, Oblivion looks great. Even after six years, the game world is full of color and lighting is just beautiful when the sun goes up or down. The only thing about the graphics are the people, they do not look that great.
Combat is much better than in Morrowind. You actually have more control of the movements and when you hit an enemy is far more satisfying. As you progress in combat skills you become more experienced in certain kind of armor and weapons.
The sound of the game is amazing. While in Morrowind you had to read the dialogue of each NPC, in Oblivion each NPC has full speech helping with the immersion and flow of the game.
If you like RPG and freedom to play, you can't go wrong with Oblivion.