I have been an eBay Power Seller for many years and have quite a bit of experience with eBay and PayPal and situations like this.
Like someone said, PayPal almost always sides with the buyer but it's usually in the case of non-delivery. If a seller can't provide proof that the item was delievered (tracking number, delivery confirmation, etc.) to the buyer, 100% of the time PayPal will refund the buyer. However, in cases of "item not as described" or as in your case, imitation merchandise, PayPal has shown itself to be quite wishy-washy. Short of going to an official retailer with your fake item and having them sign a statement that say that the item you recieved is indeed fake PayPal is not likely to refund you. Cases of "item sufficiently different than described" are even harder for the buyer to prove and usually result in a claim being denied. Not too long ago I purchased a Dolce & Gabbana mainline suit from a seller who claimed that it was a black suit as described despite his pictures making the suit looking medium gray. Sure enough, I recieve the suit and it is indeed gray and with a closet full of gray suits I had no use for it. The seller refused to refund me and PayPal denied my claim as well. Anyone want to buy a suit?
My advice to you in this situation is that if you used your credit card through PayPal file the claim with your credit card company, not PayPal. They're much more ruthless and have almost a no questions asked policy regarding customer disputes. Everyone should follow this advice. PayPal does everything in it's power to have you use the "Instant Bank Transfer" option when sending payment. Don't listen to them, it's in their best interest that you do so, not yours. Use your debit card or credit card through PayPal. Visa, MasterCard and AmEx will all take much better of your than PayPal. In fact, a few years back, PayPal had a class action lawsuit filed against them for their poor performace protecting buyers.