Each film is to some degree worse than the one before it, so a ranking from me would be pointless as it’d just be me listing the films in release order.
Raiders is a perfect film.
Temple is the rare sequel that tries to do something very different to stand apart from its predecessor, and while there are a few missteps it’s mostly great.
Last Crusade is the standard sequel that rehashes the popular first entry while Flanderizing all the characters to death (especially poor Brody). It’s saved from being garbage by Sean Connery and the last ~30 minutes, which are genuinely fantastic.
Crystal Skull isn’t as awful as its reputation but aside from a 20-30 minute stretch in the middle of the film, it’s not very good. I disliked that they brought back Marion, tying it too heavily into Raiders instead of letting it stand on its own. And far too many moments in the film are utterly cringeworthy.
So, for me:
- Raiders: 10/10
- Temple: 9/10
- Crusade: 7/10
- Crystal Skull: 5 or 6/10, I can’t really decide.
Switch The Last Crusade and Temple of Doom and you have mine. I think Temple of Doom is as dark as it is due to Lucas going through depression during the development of the story.