The quality of your render is not determined by the machine but by the codecs and the software you use. A computer may be slower than another depending on processor/cores/speed and RAM. For encoding video for the web use Adobe Media Encoder or other packages like Xilisoft. Render from AE uncompressed and then compres for web.
No the CPU doesn't make a difference in how attractive the render is. It's the software settings and the craft that make something more attractive.
There is either something else missing in the equation when you render...maybe some post color grading...
Alternatively...perhaps you are comparing the quality of the image based on different monitors? For instance, did you look at his work on a beautiful new LED monitor, and compare it to your work that you are viewing on an older, drabber monitor?