Is this a good breakfast??

I would think that if the entire amout your eating is equal to one serving size (usually for cereal its either 1 cup or 3/4 cup) then you should be fine. Its good that you are eating breakfast, but I would try to add a little protein or something too. What about doing a non-fat yogurt if you don't like milk? Or do a piece of fruit or something so its not just the cereal. Breakfast kick starts your metabolism, so don't be afraid to do a little more if you need the energy. You have to have an entire day of balanced meals to maintain weight, its not just the breakfast that will determine it.