If you have hard water, glasses can look spotted and cloudy even after cleaning. Sometimes changing the dishwasher detergent can help. The easiest solution to clearing up glasses that start to look cloudy is to add some vinegar to the bottom of the dishwasher before you start a cycle. Simply add 1 cup of white vinegar and it will clear up your glasses very well.
You should see marked improvement after the first time you do this. If they are not crystal clear then simply repeat the process until all of the cloudiness is gone. In fact I recommend to using a little vinegar in each cycle to maintain the clarity of the glass.
Note: you can pre-test this by rubbing some vinegar on an individual glass with a cloth. If you cannot remove the cloudiness by soaking it and rubbing vinegar on it then it is possible that the glass is etched due to harsh or cheap dishwasher detergent and vinegar will not solve the problem.