I should point out that the Top 3 are all 10/10 movies for me, so ranking them is kind of pointless.

Raiders- Perfect escapism. Perfect hero, perfect villain, perfect action set pieces, an engaging plot line. Good balance between intensity and humor. What else is there to say?
Temple of Doom- I like that they took risks and tried to do something different. It’s such an insane ride. Of the four, it feels the most to me like a 30’s adventure movie.
Last Crusade- Used to be my favorite and I do still really love it (mainly because of Sean Connery), but I like the intensity of the first two more. I will say though, this one is the funniest of the series and probably the most quotable.
Crystal Skull- I don’t think it’s as bad as some say, but it’s not good either. Has its moments, but it’s pretty lackluster. It loses me around the halfway point. I didn’t think the plot or action scenes were that great. Hopefully Dial of Destiny is better.