There are not many good alternatives to a jailbroken apple tv 2 out there! Some options are a Roku box with plex which still has many limitations and is unable to run XBMC. An android box or stick is another alternative to a jailbroken apple tv 2, however, XBMC is still being developed for android and I feel android is not quite ready to be used with a tv remote. There are also a countless number of other boxes out there that are trying to re-invent the wheel.
A Jailbroken Apple TV 2 is now so popular that it costs 3-4 times more than the original value it sold for! The only current alternative to a jailbroken apple tv 2 is the Taffy Media Center. If you want a reliable box that “just works” the way you would expect it then this box is for you.