The main issue with the majority of these:
How can you have such a good outline and shape of something and have almost no real idea how it's colored? And how could you have gotten this good in such a short time?
Come on, if you know how well something is shaped, you should know exactly how it looks in a 3-D perspective, that's an important thing to know when it comes to this stuff; slapping gradients everywhere just sort of ruins it.
That's why they seem traced/copied/yadayadayada, do you kind of get it now?