Thanks Ingmar.
I also forgot to mention that I found my authentic GTA IV wanted poster and I compared it to the ones that I bought on eBay recently. Well, it's just like I thought. The ones that I bought from eBay are different than the real one that I have. The authentic example is of superior overall quality. On the authentic poster, the balcks are deeper, details are way sharper, the whole image is bigger, and the paper is slightly smaller. It looks to me like the seller simply photocopied the genuine posters. That's what they look like; photocopies. Of course, I have no way to prove that they're fake. All I can say with certainty, is that they're of inferior quality and are probably not real. I find it hard to believe that Rockstar would put out this poor a poster. For all I know though, they made these in all kinds of sizes and quality...
Here on the right you can see the genuine poster versus the cheaper poster on the left:
real poster on top, cheap poster on bottom:
