I was captivated by Vulcans for a very long time, but since they've been done to death (get it?) that has waned some. I am also still
intrigued by Andorians. I mean, c'mon, they're blue and have antenae! For the same reason I also dig Edosians and it was cool to see one in the new film.
In recent years I've added Trills to my favourites box too.
For villains, Romulans still hold the greatest appeal, but with the reboot and a chance to explore a new relationship in the Klingon Empire, they may interest me a little more, but I doubt it.