From the Painting Guide: I think pencil crayon, like watercolor, is an easy medium to use at a basic level, but takes persistence to master.
The first thing that strikes me about this artwork is that is needs more color laid down; there's too much of the paper showing through and the color isn't strong enough. Take a look at the intensity of color in the colored pencil artwork by British artist Katherine Tyrrell, and you'll see her colors sing and vibrate. That comes from the layers and layers she applies, building up color to reach this final intensity.
Things to Consider When Looking at This Painting:
Creating a Sense of 3D: The illusion of depth in a painting is created through the use of tone, or lights and darks. As I said with your apple painting, exactly where these tones are depends on the light direction and the subject. To internalize the concept, start by painting a few spheres, or balls (read: Painting Basic Shapes: A Sphere). Once you've got that working, transfer the knowledge to your pineapple and pear, which are like an elongated sphere.
Composition: Have you noticed the tip of a banana sticking out behind the pineapple? Do you think it adds interest to the composition, or is a distraction? Its curve does echo the curve on the edge of the plate, but I think it needed a bit more of it showing, for it to have more of a definite presence in the painting.
For more information on using colored pencil, see this collection of Colored Pencil Drawing Resources from About.com's Drawing/Sketching Guide.