There is a huge amount of back history to both the Hobbit and LOTR and it will therefore be interesting to see what they leave out, rather than what they include. There is more than enough material to cover dozens upon dozens of films, and a good chronology of the events can be found here:
I'm a huge fan of the world that JRRT created, but it is a very detailed fantasy world, covering thousands of years, and I can understand why some people have neither the time or inclination to lose themselves in unravelling it's history.
No film is ever going to recreate the images that I visualise when thinking about the different ages of Middle Earth, but I do enjoy getting a glimpse at some of the things that other people imagine. Now that the technology exists to recreate Middle Earth on film, we will hopefully get to see more and more films over the coming decades, each revealing a new glimpse into someone else's imagination. There will be films of the proud Numenor and Noldor, as they fall under the influence of the supposedly repentant Sauron, as he secretly forges the nine rings. There will be films about his master, (Melkor), as he battles first the Valar and then the Elves. The potential list of major events worthy of a film just goes on and on, and I would happily sit through every single one of them, if they are of a similar quality to the Jackson films. I don't agree with all the choices that Jackson made when casting and filming LOTR, but that didn't stop me from enjoyng the films for what they were. I hope that the Hobbit films are a huge box office hit, because I want to see more of Middle Earth, regadless of whether or not I like Jackson's version.
If there ever was an after life, then I would happily settle for Middle Earth. I have journeyed across its lands so many times, wondering at it's peoples and spectacle, that it's now a part of who I am.
Regards - Mr P