I think that it is hard to judge to in an objective and analyze in subjective way. Every person can say "I like it", "it looks ok for me" or something like that without having artistic knowledge (or graduating from an artistic school) If someone has such knowledge he or she could say that the colors are ok, brushes are fine and so on. To sum up, as far as art is concerned we should focus on our own feelings and subjective way (I like it, the best part of this picture is...) and so on, if we know something about art we can of course add it