Aye, you definitely have a point there.
Me next door neighbor's kid, Matt, is an only child and gets everythin' he wants. My son (same age) is the smallest of 3 and has grown up learning to share, take turns, clean-up, etc. I had to teach Matt to clean-up the toys before he leaves - he started with telling me he couldn't cause he had to go home right now. I had to teach Matt to share and take turns. His mum would actually take a toy from my son if Matt wanted it - yeah, had to teach her too.
Now, you couldn't really blame the kid, cause that is the way he was raised, he just had that "only child" syndrome. It has definitely been a learning process.