I personally feel that Crusade is the least of the original Indy films because it's rather repetitive; the villains are Nazis once again, and the MacGuffin is another Judeo-Christian artifact; IMHO it would have been better to have used another group as adversaries and/or used a different MacGuffin.
That being said, my impression of the film has improved greatly over the years; KOTCS helped to put things in perspective.