Question about Oblivion

Technically yes.
You could join just one faction and do as many of the quests as you want and come back later.
Or you could just roam around doing as many side quests as you feel comfortable with.
A lot of the side-quests are organized by theme in a series, too.
Don't have to start the main quest until you want to and even if you start it, you can delay any mission as long as you want.
Basically you roam at will doing whatever you want whenever you want; there is no specific order because the opponents and rewards scale up with your character's level.
However, all that is technically.
In practice, the game is addictive enough you likely won't *want* to stop. ;-)

If you can find it used for $20 its a good deal.
The original release is currently running $30 as a Platinum edition.
And the GOTY version just shipped with both Knights of the Nine ($10 to D/L) and Shivering Isles ($30) included for $60. Knights of the Nine is an extra faction Quest-line with some pretty clever puzzle quests in the mix, Shivering Isles is a whole new realm with its own logic, creatures, and gear to explore. If you want the full Oblivion experience, GOTY might be the way to go...

A warning, you will get nowhere in Oblivion if you don't have 1-2 hours per session to put into it.

Oblivion is a must have

fjtorres is 100% correct.I have invested over 100 hours into this game and can say that it allows you to play in small or large pieces. The best part is that you can save anywhere in the game so you are not forced to keep playing untill you get to the next checkpoint.

I do recomend this action RPG.

i've got 150-180 hours in this spread over a year or more, easy to jump into any time i want to play it, i still haven't really delved into the main quest, and still hoarding ms points for the expansion, eventually i'll get it all finished, but for now i'm enjoying picking some up here and there, it's nice to be able to do that.

Just started the GOTY edition last night, and I bought all of the additional content from the marketplace. I know this will be one huge, fun experience. Once I have MASS EFFECT, I'll be doing some serious time traveling back and forth. Excellent!!!!!!!!!

Oblivion is such a massively huge game (especially when you consider the downloadable content including the huge Shivering Isles expansion pack) that even if you played it 30 hours in a row, it would still feel like you were just popping in for a bit and popping out. There is so much to do, and so much freedom in what you do when, that it can easily be enjoyed in short bursts from time to time, set aside, and returned to much later. It's certainly not a game where you feel like you can finish it now if you just power through for a little bit longer.

The real issue is this: it is entirely possible to play in short bursts, but highly improbable that one would be able to do so! It sucks you in so well that it is very tough to put down once you get going in a session.

qft

I bought it on release day and I still play it religiously.

I must have logged over 1000 hours since release.
I just wish it had a co-op mode or a character VS online.

I've had Oblivion since it was first released and playing it off and on is exactly what I've done with it. It's a very good game and it gets you pulled in quickly and the controls are easy to learn so I definitely think that it would hold you over until COD4.