I found that the difference between mixing the cereal with water vs. whole milk was huge in the taste department. Also, my son didn't seem to like the oatmeal one and loved the rice one, whereas my daughter will eat both but favors the oatmeal. Both seem/ed to like it better when I make it with whole milk over water. The cereals with the fruit seem to go over better too.
Another thing is texture. One other mom mentioned the cereals seeming like goo - made the way the box tells you to it sure does! I tend to like my own oatmeal thicker, so I tend to stir in more of the cereal until it gets to a consistancy I would be more comfortable with. Both my kids have seemed to like it thicker as well.