My daughter is 4yrs old and she watch TV very often. I dont think she is self-centre, in fact, she learn most of the stuff on TV.
In Canada, we have a Treehouse (I think similar to cartoon network in HK) and this is 24hrs channels. All cartoons are educational and very positive. I never seen any violence from there. I always watch with my daughter as this is the way I can understand her world. She always come to me and asks me "do you remember ...?" -- which she refers what we have seen on TV.
She is the only child in the house and we both working, so hardly has anytime to teach her things, however, she seems pick up alot from school as well as TV.
Besides TV, she likes to rent DVD from library, each time 10DVD and she can watch it in her room for half day without disturb us at all.