The Persona series actually only has the barest relation to the Shin Megami Tensei series, it's just that in the West they label nearly everything made by Atlus with 'Shin Megami Tensei'.
I liked Catherine. At first *boner* :D When she turn into a gigantic monstrosity *boner down* D: Getting the True Catherine Ending *Boner Revived!* >:D