I've seen the first three Indiana Jones movies. I loved Raiders of the Lost Ark. I liked Temple of Doom a lot more than most people did. My memory of Last Crusade is that it didn't live up to the first two, and in fact I've never seen any of the subsequent movies in the series. My grandson was over, and he wanted to watch Last Crusade, which he likes. I still think it falls short of the first two, but I need to get past that negative statement, because Last Crusade is a perfectly serviceable film, one that a 10-year-old can watch with ole grandpa and know they'll both be entertained.
There's a bit of been there, done that about the third film in the series, and since the original was a highly enjoyable pastiche that bragged about its been there done that nostalgia, it's a case of going to the well one time too many with Last Crusade. But my grandson hasn't seen the other Indiana Jones movies, and he doesn't know the movie tradition from which Spielberg was drawing, so it's all fresh to him.
All of the films have an uneasy relationship with faith, explicitly here since everyone is searching for the Lost Grail. It's as if Spielberg wasn't satisfied with just a great action picture, so he added a little "depth". I imagine this is one reason we get Indy's dad in this one ... nothing like a little easy character "development" to add that depth. And Sean Connery is fun ... you believe he's Harrison Ford's dad.
As always, there are some wonderful set pieces. If you don't set your expectations too high, you will enjoy Indiana Jones and the Last Crusade.