Raiders of the Lost Ark: 10/10 The first, the best, and the one they've all been compared to since, but failed to match!
Temple of Doom: 9/10 Not nearly as perfect as Raiders, but still comes in a close second in my opinion. One of the best movie sets of all time, not to mention the most badass version of Indy yet. All I have to say is, "Mola Ram, prepare to meet Kali, in HELL!"
Last Crusade: 8/10 Fun, but too much of a retread of Raiders at times. Henry Sr. though makes up for a lot of that. Also, what a fantastic ending!
Kingdom of the Crystal Skull: 6/10 It was great to see Ford donning the fedora again, but the weak script, lack of suspense, and painfully unfunny moments (or unintentionally funny) knock this one further down the ladder.