Depends on the money you want to spend. Hotel Majestic is great and in a perfect place near Plaza Catalunya, Hotel Arts is maybe the best in the city, in front of the sea, less interesting place but with good connections, you can even walk to the Ramblas if you like walking. Hotel Omm is a good option too. You can find cheaper ones near the Ramblas like Hotel Turin or around there. For romantic quiet weekend Arts is a great option, you have lots of restaurants etc around. But of course if you plan to move a lot and see the city maybe the Majestic or Omm are better options, and really romantic too. You can check their sites!