THE WITCHER! I have vouched for this game several times and will do so again gladly! I believe it fits virtually all of your preferences. And it was widely regarded as the best RPG of 2007. The story, atmosphere, and characters are all top notch. Some of the translation is a bit sketchy, but really, it's not bad at all! This game is focused much more on plot development, immersion, and atmosphere than looting and leveling up, and there really isn't much new gear/equipment to be found. I personally don't care about this at all, but there are some people who are more into customization than character/plot. It is also a very adult oriented game in that there are very mature themes, ideas, and situations, including some sexual content. Just to give you a taste, here's one of my favorite, albeit a slightly cheesy, lines so far:
"Sex, politics, politics, sex...they both come down to one thing: f****ing others!"
Furthermore, the developers of The Witcher are soon coming out with a new content patch known as "The Witcher 2.0" which is a fairly extensive redesign of the whole game...FOR FREE! It will include a whole slew of new character models, improved load times, and will largely replace the current translation, with which the developers weren't completely satisfied.
As per your request on time, I have been playing The Witcher for several months and still haven't finished. This is largely due to the fact that I CAN just hop in for a few minutes and collect a couple of quest items. At the same time, I've had a couple ~5 hour sessions, which is usually when I delve more into the plot related quests.
One final note, the camera view can be switched from 3rd person isometric to over the shoulder...im sure you can find something you like there.