Hotel in Paris--is a whole book, there are tons of them out there. You'll have to do some research before anyone can begin to recommend something for you. What arrondissment are you interested in? If you can't narrow it down to that --how about rive gauche or rive droite?
There are tons of deals out there now in Paris, but need to do some homework. Always best--IMO to go right to the hotel's website.
A good start is the website Trip Advisor, read hotel section. Will give you lots of ideas in every price range.
Once you get started, ask some more questions and then we can probably be of more help.
And agree w/ above poster, not real fond of Athens either, but many are so wouldn't give up the idea.