Camp. I suggest you do some more research, and just spend some time rendering different materials, until you understand their surface properties more. Also, go for a more dramatic lighting scheme, to help define the shapes. If you have any 3d package (you can download Gmax for free), use it to explore different materials.
The highlights on the arms seem too focused, and white. Pick a light source, and think about what shapes that light would be defining. The highlights should be more diffused and broader, being brightest only where the planes directly face the lightsouce. (play in Gmax with objects, using facet-highlight mode in your viewport, to see how the highlights react in relation to the plane angle/ light direction). Also, it's a good thing to always add some sort of lower contrast bounce light, that helps define the contour of edges facing away from the lightsource.
The armor needs more highlights, for definition. Once more, establish a lightsource (for a game model, it would probably be coming from the sky), and use that information to build depth.
Analyze everything you see, and try to understand how light defines it's basic shapes. Once you have a handle on that...move on to color. Work in grayscale for a while...this should simplify your tonal studies.