Hi there. We have one son and we are happy with just that. Honestly you can't win with some people no matter what option you choose so you have to do what feels right for you. I have great memories of my childhood and I have bad ones too. Some kids really suffer because of their siblings and some are really close. You can't guarantee either way. Only children tend to get more one on one time with their parents which can be really beneficial for their development. But of course that is up to their parents to provide as well as playtime with other kids.
As for being spoilt people are often mistaken as to what spoilt is. Kids don't get spoilt from having their parents attention and love. They get spoilt from not being taught boundaries and compassion. It really has little to do with whether you have siblings or not. In fact I think sometimes it can be easier for only children as they don't always have to compete and feel threatened about things being taken away. I have real eating issues because it was always 'eat now of forever hold your peace' when you have two older brothers. LOL

Anyway not sure if the rant made sense but that is my point of view. Hope it helps