Most of them look good if not having the polish of studios specialising in computer animation (Pixar for one), often great music, good lessons and messages, a good deal of charm, have their heart in the right place and have entertaining characters well voiced (some had actors of considerable calibre like Tim Curry, Anjelica Huston, Martin Short and Kelsey Grammar, all of them terrific in their respective outings Curry especially) and a likable title character that particularly young girls can relate to. Are they worth watching if taken for what they are? Absolutely for most of them.
Are they among the best films ever made? Again no. Despite not being the main target audience, to me they are mostly better than given credit for, easy to take them for what they are and don't deserve to be dismissed as baby-ish and for little girls only (a very narrow minded generalisation). It is understandable to take issue with the dialogue (a fair few are ropy in this regard), the predictability of the stories, the odd annoying character, the animation in a few (not all are well animated) and whether there is enough for adults to keep interest. It is very easy to meet the 'Barbie' films with a lot of dislike and scorn and they are all very lowly rated here (despite some favourable reviews).
