Portrait styles and trends?

Photography seems to be like anything else out there in that there are trends and styles that come and go.

So my question is, what style/type of portraiture photography do you think comes closest to what may be called a "classic" style - one that transcends time and doesn't tend to date itself?

Three light business headshot on a gray backdrop.

LOL - I have to laugh because my dh is soon going to be having his updated for real estate.

I don't think there's another word for it, it's Classic or it's not.