I would argue that Aristotle improves some of Plato's philosophy but that he also causes some problems with his theories about science. First, Aristotle certainly makes Plato's ideas more accessible to scholars and to the common man. Plato provided the basic elements of Idealism, and Aristotle takes those elements and applies them specifically to rhetoric, literature, ethics, etc. Aristotle's writings, especially in regards to persuasion and drama, are the basis of much of how we write and critique even today.
One problem, however, with Aristotle's "improvements" on Plato's philosophy is that in our current science-weighty world, Aristotle's ideas regarding research, astronomy, etc., are elementary at best and can cause modern students to question his application of philosophy to other areas (since he was so flawed in scientific thinking).