Well, technically it's all unreleased. Instead of releasing just a greatest hits of the songs from the previous albums, they remixed most and re-recorded some of the songs. The digi version has a third disc which contains a 're-worked' version of the Lucifers Heritage demos plus other demos. This is why I want this version. Even though most BG fans have these from some bootlegs, having an official good recorded version is awesome.
I don't want to take up too much room on here so I won't post the track list but here is a link with more info.
http://www.blind-guardian.com/2011/11/10/memories-of-a-time-to-come/