They've come to you because you are an "expert".
That is bad practice, you should want to produce great work, that is how you keep clients and get new ones, it also makes you better, do you want a portfolio full s**t?!?!
Try to distill what the client likes about the sites instead of a blanket statement like "I want to look like this". Then you can work with these comments to aid your design. Another way is to do two designs, what they want and then do an improved version that of course looks much better, this works most of the time and eventually they trust your judgment.