You don't have to like the RPG genre to enjoy this game.
This game is truly amazing. The main story/quest is exciting and interesting, there is not a boring moment. And all the side quests are really fun, if you become popular enough by doing a lot of side quests, that just leads to more quests. Factions (Fighters Guild, Mages Guild, Thieves Guild, etc.) also keep you busy doing Duties/Contracts. You can make big money doing it too. There are so many different quests that it's hard to keep up. I recommend getting the game guide for this. IT HELPS A LOT because it has a walk-through for every quest.
There are over 100 hours of gameplay added to the already high 200 hours of gameplay (that's over 300 hours of gameplay for those who are confused, haha). I, myself, have put in over 150 hours of gameplay and I haven't even finished 1/4 of the quests yet. There's just so much to do.
Cyrodiil is an enormous place. They put a lot of detail for when you decide to do some traveling. You can find new places like mines, caves, old forts, etc. There are also bandits that camp out near roads, and they will attack you if you get to close. If you don't feel like walking the countryside, you can always 'fast-travel' to any of the 9 major cities: Anvil, Bravil, Bruma, Cheydinhal, Chorrol, The Imperial City, Kvatch, Leyawiin, and Skingrad. You can also use 'fast-travel' to any of the locations that you've found (to mines, caves, old forts, etc.).
What is really cool about this game is the way the NPC's lip-sync what they say. It's a lot less boring than having to read what people are saying and it adds social interaction, like you are really talking to someone.
In the end, Oblivion is simply a fun game. You can spend hours exploring the land of Cyrodiil, inside the major cities, or spend them helping out the townspeople. It's what a Role-Playing Game should be.