There are so many more tangibles outside of "good" in terms of quality of film. It might even be the least likely qualifier. It's certainly a better film than despicable me- but which is more marketable? Likewise, Cars is arguably the weakest of the Pixar films yet it's a beast in terms of merchandise. Superior films like Up, Wall-E, Rat, etc can't even compare.
A good theme park land is also separate. Cars, again, is a great land.
So in summary: marketability, popularity and a thematically sound land will outweigh what was a good movie any day of the week. It doesn't need to be a good movie to be a successful land, although it doesn't hurt.