We stayed a week at Ottleys Plantation Inn and highly recommend it for as an hotel or just a meal. To us beaches did not compare with BVI or other islands we have previously sailed through. However a trip to Brimstone fort is well worth it. We went as part of a day long tour and were surprised that we could have happily spent considerably longer there than the allotted time. Not far from there were some beautiful gardens and store where they make beautiful batique items. Well worth an hour. As others have said, you can take the sugar train, only operates on cruise ships days so is busy, but it is apparently good fun and you get to see much of the island.
Why bother visiting other islands if you want them all to be the same? We won't visit St Kitts again, but enjoyed our time there. It will suit others far, far more than it did us, but we gave it a good try.