Ok you are right. If i lower the Resulution of the background images it works fine when i add another gamelist.xml file.
Although adding a new system with more roms breaks the system again in the known too few ram fassion directly at startup.
Still there must be a MAYOR Ram drain if a single gamelist (which shouldt be affecting the overview and should only be read when entering a specific System).
My tests indicates that at the Moment, emulationstation parses every Gamelist.xml file directly at startup and keeps everything in Memory.