If you've seen The Adventures of Tintin by Steven Spielberg, you've probably already heard of the story of how he acquired the rights to redo the Tintin books on film. Since the anecdote would require effort on my part to paraphrase, let me just lift it directly from Wikipedia:
Spielberg has been an avid fan of The Adventures of Tintin comic books, which he discovered in 1981 when a review compared Raiders of the Lost Ark to Tintin. His secretary bought him French-language editions of each book, but Spielberg did not have to understand them: he immediately fell in love with its art.
This then renewed my interest in the Indiana Jones films, which I've loved ever since I was a kid. In fact, at one point in my life, I wanted to be an archaeologist, especially after The Last Crusade and Jurassic Park. That's another Spielberg film. It might be safe to say that half of my childhood fantasies were directly or indirectly influenced by Steven Spielberg.
Anyway, this review will try and see what it was about Raiders which prompted the French to cry "rip-off!"