I know I'm a bit late to this particular party, but here-a-goes:

I remember Last Crusade being the best of the Trilogy... but I haven't actually watched it in 15 years or so. I did watch Raiders semi-recently, and perhaps my adult sensibilities are able to recognize this as the superior film. A younger version of myself will agree that Raiders has a lot of downtime (the University, the explanation of the Ark, meeting Marion, a lot of sitting around in the desert) which said younger self found fairly dull... The older and wiser me now finds these scenes to be much more interesting and to some degree the heart of the story.

I also wonder if a lot of my fondness for Last Crusade came from the video games. I played both the Action Game and the Adventure Game that Lucasfilm Games released at the time (and the follow-up Fate of Atlantis!). I knew the story of Last Crusade a lot better than the other 2 for the sake of playing through the games.

4 was terrible. I wish it would have been more terrible, so it was more clearly in the wrong. There are people who liked it.