On my last trip to Paris I stayed in two hotels I liked enough to share. Neither are fancy or luxurious. However, they are both well above a hostel or budget option. And I would definitely consider both again on future trips.
Mercure Raspail Montparnasse – This hotel is in a magnificent location close to Monparnasse station in the city center, several metro stops, and Luxembourg gardens. There are dozens of restaurants within easy walking distance along with some excellent bakeries for breakfast (and late night snack). Rooms are small (but not usually so for Paris) but do a fantastic job of maximizing space. The bathroom was larger than should be expected and the staff was friendly.
Hotel Eldorado – This small hotel has tons of charm. Upon arrival you think of New Orleans but really New Orleans should make you think of here!! The hotel is a couple of minute walk from the Place de Clichy metro and has easy access to both Moulin Rouge and the Sacre-Coeru Basilica which gives amazing views of the city. The hotel has a beautiful garden and a popular restaurant next door. Ironically, I loved that I had a room with a shared bath. While my room had a private toilet and sink, the shower was down the hall (they do have rooms with a private bath). This was actually ideal for me as I arrived early morning after an overnight bus ride and my flight left late at night a few days early. The amazing staff allowed me to store my luggage before & after checking in and the shared bath allowed me to clean up!