I once saw a fascinating program in Germany about large families (10 children minimum). One mother was even a single mother whose ex-H had moved abroad 
Anyway, no the children didn't get much one on one time with the parents, but they had equivalent support/love etc from other siblings. Only in 1 out of 5 families did there seem to be a real problem with jealousy. The 3 eldest girls were jealous of the time, love and attention given to the 2 youngest children.
It's a different childhood that's for sure, but I don't think we can say it's worse than being an only child, or one of 2/3/4.
The parents were very impressive with their routines and feeding of at least 12 mouths a day!