Imitation is the sincerest form of flattery. And when it comes to the movies, it's pretty much inevitable.
Nothing wrong with that; trying to duplicate a successful formula is not only human nature, it's good business sense. In the movie biz, that means that when one film is a runaway success, others like it will be sure to follow.
But if you're going to follow a successful film's suit, can't you please follow it well? Can't you please put enough care and thought into it that the resulting film could, if necessary, stand on its own legs?
Too often, that's not what happens. Case in point: Eragon, opening today, is a wan imitation of The Lord of the Rings, with more than a few Star Wars bits thrown in. But the resulting film seems as it were made by people who never understood what made the original movies so successful. It lacks scope, doesn't develop any of its characters and believes that just mentioning magic, throwing a couple words around and having an old warrior mentor a young one will be enough. The result is one of the year's most disappointing movies.
It doesn't have to be that way. When Raiders of the Lost Ark came out in 1981 and made a gazillion dollars, Hollywood took note. Three years later, Romancing the Stone came out. The earlier film's influence was obvious, but Stone had its own strengths, too, including a talented cast (led by Michael Douglas, Kathleen Turner and Danny DeVito) that was obviously having a grand time. The film was lots of fun and turned out to be a major hit.
See what's possible when you put enough thought and care into things? Even knockoffs can look reputable and turn a profit.