i saw the first one in the theater...and like you was not all that impressed....basically cutting straight from the show with a bit better animation and some of the fights and Angels were different
but the second one kicked ass....new characters...one of which (Mari) almost replaces Rei as my personal favorite character of the series and by the end it sets up for a completely new story and a good one
the third is completely new
worth checking out if your a fan of the show