Everyone knows about the Hockney, but there are several other interesting exhibits in Paris right now.
Artemesia Gentileschi whose 'Judith and Holofernes' (Uffizi) is well known has a wonderful exhibit at the Jacquemart Andre. I had only seen a couple of her paintings; this exhibit must have 20 or so. they also exhibit work by her father and by her contemporaries like Carravaggio. Excellent and the Jacquemart Andre is also a lovely old mansion and has a good tearoom for lunch.
The Picasso has a current exhibit on 'Degenerate Art' banned by the Nazis. It is amusing to see what they considered 'degenerate' -- basically it is any art created by Jewish artists and modern art.
the community museum in Nogent sur Marne has an exhibit of Willy Ronis photos; he was a fabulous photographer of paris scenes after WWII. You will probably recognize some of the photos as he created many of the classic what it is to be French photos.