Garage floor paint is more than meets the eye.  To get the best paint for your garage floor takes a little research and time.  Using any concrete paint will not last long and will be a cheap way to cover your floor.   The best type of paint is epoxy paint and it will cost you more money per gallon.  Any other type will not give you the bang for the buck that you will need.
There are many manufacturers that produce paint.  The ones to buy might be the companies that have the best reputation. Companies like Behr and Quikrete both have readily available paints, and are at a cost of about thirty dollars a gallon. Your local Home Depot or Loews should carry them.  Are they worth the time and effort to use in your garage?  I have heard complaints and also good reviews on both and I suppose it all depends on how the prep work is done on the floor and the quality of the paint.  If you are going to invest into a paint that you want to last a long time, companies that specialize in garage floor paint are probably a better choice, especially if you own a beautiful car and you want a good surface to compliment the autos shiny paint and smooth curves .
Water based paint is substandard to a solvent base paint. The idea of covering your floor and sealing it is the key to a successful paint job too.  If you are getting moisture from a moisture test then the recommendation is not to use epoxy paint.
The best garage floor paint should not be something that should be cheap, but you should be able to spend a little more money to get the results you want.  In the long run you don’t want the aggravation of redoing the job over again.  Hiring a professional contractor could cost around two dollars to four dollars a square foot. Buying good quality paint from a specialty company will be less money then a professional application and you could save thousands of dollars and have a floor that is very similar to what a professional may complete.  Buying lower cost paint from a local store may work, but you have to consider the longevity of the epoxy and the long term use of the garage