Just how much do lighting and rendering techniques affect your work? Well - quite a bit.
As Lucy Burton states in her tutorial, Simulating Real-world Film Lighting Techniques in 3D , "Good lighting and rendering can make even a simple 3D model look extraordinary, and poor lighting can make even the best model look bland."
As games become more and more cinematic in look and feel, a firm grip on light placement, intensity, color - as well as techniques and technologies involving Global Illumination, Final Gather (FG), Ambient Occlusion and high dynamic range imagery becomes more and more important to the Visual Arts side of game development. Check out Lucy's work in the Artist/Animator Community.