Moderator's Note: This thread was split from the "Best Paintings at the Met" thread.
Okay, now you've got me started:
"Best Paintings in Paris" (in my humble opinion...)
In the Louvre, "Botticelli's Spring", a detail of which is shown here.
In the Musee d'Orsay, A Bouguereau entitled "Night". I can't attach it because it's a nude. I also can't find an image of it on the web. It's part of a series and you can do a Google image search on the words Bouguereau and Evening if you want to see one that is very similar.