Literature professors theorize about a lot of stuff, including the question of which audiences lust after which fictional characters.
I don't know which professor originated the theory, but I believe the literary theory that most audiences lust after fictional characters who are reflections of the audience's ideal self-image.
The typical example would be the hero of a typical bodice-ripper romance, who is often a slightly modernized version of Heathcliff (who reflects female passion) or Mister Darby (who reflects female desire for stable relationships).
In anime, I would expect male heroes written by female mangaka to appeal strongly to female ideals. I haven't checked to see which mangaka are women in most cases.
Example 1: Lelouche. He is a natural leader of men, and many women want him for his obvious strengths. His most important romantic foil is kept vague, so that the female viewer can imagine herself as loved by Lelouche. His most important power - to command obedience by a kind of super-charisma - corresponds to female fans who pride themselves on persuasiveness.

Example 2: Edward Elric (written by a woman). His tragic flaw is loyalty to his mother, his primary goal is to rescue his brother, and his secondary goal is physical health. This reflects female desires for strong family loyalties.

Example 3: Vanilla, from Galaxy Angels. She is cold and sardonic, but dutiful, religious or mystical, and intelligent. She sometimes acts maternal, suggesting that she is mature enough to become a wife and mother. Her biggest fans are probably men who want to get married and who are trying to save up money, who see themselves as dutiful, self-denying, intellectual, etc.

Example 4: The blonde telepath from "Book of Bantorra." She is idealistic, dutiful, militaristic, and intensely loyal to her man. She reflects the ideal of a man who sees himself as dutiful and committed to sexual faithfulness.

Example 5: Priss from Bubblegum Crisis. She is individualistic, proud, irreverent, given to improvisation (regardless of whether she's rocking out or kicking butt). She appeals to the extroverted would-be punk-rocker boy, who has not yet given up on his dreams of glory.

I imagine that the bishounen of Boy-Love books represent some ideal of the women who write and read those books, but I don't know enough about them. I know a lot of straight women who like stories about gayish-but-not-quite-gay boys, who are repulsed by explicit gay male sex. To me, this suggests that the gay male character is a symbol of some hetero female virtue, not a real depiction of a gay man.

The Empire of Corpses Gorily Grim
One Piece: Burning Blood Total Bikini Madness
Bakuon!! Wild & Rough
Milky Mimi Ero-Figure Deliciously Creamy
Dead or Alive Ero-SFM Doubly Dirty