If you really think about it, it's not un-natural for two humans that have gone through puberty to be sexually attracted to each other, what is "perverted" is sexual attraction to someone who has not developed sexually, it's a perversion of the natural order.
People get way too crazy about this stuff. It's clearly not the case that someone magically turns from a child to an adult on their 18th birthday, or that an 18 and 1 day old guy fucking a 17 yr 360 day old girl is a not a "pedophile" so there are some degrees and shades of gray here.
I think a mature adult having romantic interest in a teen shows they have some mental/emotional issues, but in terms of sheer physical attraction, it's not odd at all. I don't think it should always be treated as a criminal act.