I grew up with the old version of Pirates of the Caribbean. Prior to the movie being made and such and I thought it was the best ride there even at that time. With the success of the movies starting in 2003 my opinion is that Disney didn't anticipate it would be THAT popular. Hence, a person who has never been on the ride is going to be wondering where Jack Sparrow is the whole time. Disney had to put him in there, the movies were just that good. People always assume the rides are inspired from the movie where as Pirates was the other way around, which not everyone knows.
However, I've always felt they did a great job of blending Sparrow into the fray. He isn't in there THAT much but just the right amount for the fans of the movie to see him and in my opinion just enough for the fans of the "old style" not to complain too much. It still is a great ride either way. If Eddie Murphy was ever added into the Haunted Mansion, then that would ruin it, but a movie franchise that has been as succesful as this one has GOT to have some sort of reference to the movie in there.