I can't think of who I'd put at the top, but it definitely wouldn't be Olivia Wilde. I definitely find her attractive, but have never thought of her as being the tops. Some of her comments from that baby article annoyed me some, too...but that shouldn't have any relevance in this particular conversation.
Kate Beckinsale is a good mention, and I'd put her above Wilde, for sure. A couple of the younger names that I really go for are Blake Lively and Minka Kelly.