All I can say is yes, I have seen Fern Gully, and changing the fairies to big smurfs can't save the weak storyline.
...however the 3d effects and special effects were what the hype was about, I can't remember anyone saying anything more than it looks amazing. Which is does. So I guess I'll give it credit where it's due. For me personally, it wasn't worth the $15 to go see.