I think Wesley saw his darker self, his darker inclinations in Lilah. They were actually birds of a feather in some ways. Lilah completely gave into her dark side. Wesley managed to gain control, get over his nihilism, self-pity. I don't really know if he felt love for Lilah or not....I think maybe he did. He loved her, pitied her, other things....
He did in fact love Fred, that's clear. Whether it was warped, idealized, obsessive or not, it was love.
It was interesting, ironic. Lilah ended up pushing Wes towards goodness. Fred, towards obssessive, almost sociopathic behavior at times. Especially right after she died of course.
...but with Fred, Wes's freakish behavior was as much the circumstances as anything Fred said or did.
We never really saw what might have been in normal circumstances. Personally, I think Fred/Wesley could have worked in the "real world". If you share someone's basic values, ideals, that can be the firmest ground for a relationship. Maybe even more so than things like mutual interests. If a couple is a match in terms of temperments and values, you've got a good start....my 2 cents.