Heh, I enjoy a lot of varied male RO personalities but I do have a weakness for the cute, exciting “bad boys”. It is by no means universal I also enjoy cute gentlemen a lot, like Alty in Keepers for example (though I have some apprehension about how the last minutes rewrite might upset his whole relationship arc and dynamic. .
In general, they need to be fun for my mc to be with of course and, as in real life, a bit of humor and playfulness can go a long way. Cute, charming, preferably on the smarter side and fun tend to be the most universal, shared characteristics of RO’s I like.
The well-written “ice prince” is a close second, assuming there’s a heart of gold underneath.
That said, I wouldn’t be averse to seeing more friendship paths, particularly with some of the women too. Just because my mc’s will never love a woman in the romantic and lustful, sexual sense does not mean there can’t be anything there.