Hahaha
Marleen is actually a popular name in Austria and Germany! But I agree with you, it is not as classic as
Marlene! The song is called
Lili Marleen.
Marlene and
Marleen are not pronounced the same in
German, as you pointed out,
Marlene is mahr-LEH-neh and
Marleen is mahr-LAYN (kind of, I am not good at explaining pronunciations). They are both common in Germany but
Marlene is a bit more common now whereas
Marleen was more popular in the 80s and 90s.
In the song it is always
Lili Marleen, not
Lili Marlene, as far as I know. I actually don't like the combo
Lili Marleen because it is just too closely associated with the song and the song is really melancholy even though it is nice.
But I agree with you,
Marlene is classic and timeless.
Marleen doesn't seem as classic to me. The worst in my opinion is
Marlen. It is used in Austria as well and pronounced like
Marleen. I think it's awful because it indicates a short pronunciation of the E, like mahr-LENN but it is said the same as
Marleen and I always thought that was weird :P