This is a massive issue. No matter what you buy children, they will always want more. Nothing you give them will ever satisfy their craving. They want everything, even the thing that they won't use and will just sit on their floor all year until eventually they agree to put part with them and something in pristine condition that has never been used ends up on eBay or in a local charity shop. (I'm not saying that it's a bad thing that things are given to local charity shops, but parents get frustrated that all that money was spent on something that hasn't even been used).
The issue is only going to get worse. Companies are going to bring out new toys and kids are going to want them. Parents feel like they have to buy for their kids because everyone else is buying for their kids and they do not want their kids to feel left out or to have less than all of the other kids.
I just think we need to teach children to appreciate what they already have and what they are given.