Those people are NOT jealous 4S owners.
As a 4 owner who wishes to have the 4S IF I COULD when the 4S came out, you can't label me as a jealous iPhone 4 owner!
Some of us really feel that the next update is really too minor for us to spend our $ on, hence the criticism. Although some of the criticism is really too uncalled for....
It is not necessary for you to get a new phone or in this case, a new iPhone every year. Yes, when the new one comes out, it is very hard NOT to get jealous of those who are getting it, but software updates pretty much make up for everything. You might miss out on some major features on the new iPhone, but at least you tasted and savoured the 'new' one when you bought it last year.
I don't think iPhones are a necessity, such that you definitely have to change it every year for the new one. Unless you are a die-hard apple fan or a extremely rich person, I think changing once every 2 or even 3 years is fine.