A recent survey of Americans documents that one third of the respondents have had crossdreamer fantasies. The survey tells us that the erotic fantasies of gender variant people are just variations of the ones of non-transgender people.
We have all seen the mechanism at work. Marginalized people are judged by other standards than those who think of themselves as "normal". If a black man commits a crime, it is because he is black. If a white man commits a crime, it is because he is a criminal. If a cis woman has a kink, it is because she is sexually liberated. If a trans woman has a kink, she is that kink.
This is obviously why so many transphobes try to reduce transgender identities to sexual perversions and "paraphilias". If a male to female crossdreamer gets turned on by dressing up sexy, it is because he is a creepy fetishist, and not because she is a woman that wants to have her sexuality and identity affirmed.
Normalcy is not as normal as "normal people" think
All of this rests on the premise that cis (i.e. non-transgender) women and cis men shares some kind of sexual normalcy that is completely different from the one of transgender men and women.
The truth is, however, that there is only one single sexual fantasy found among trans people that is not found among cis people, and that is the arousal that might follow from the fantasy of being transformed into your target sex or real gender.
Such fantasies, which I have referred to as "erotic crossdreaming", most often lead to that transformed person having sex in some way or the other, most often in a way that affirms their new gender status.
There is an obvious explanation for why this fantasy is not found among cis people: They already have a body in alignment with their experienced gender. A transformation that allows you to have sex as yourself, is therefore not arousing.