Crystal Skull's fridge scene was silly and the stuff about aliens seemed foreign to the Christian religious mythos of the series. Totally unlike Temple of Doom, with realistic scenes like falling out of an airplane and hitting a mountain being okay because you're in a rubber raft, and evil Hindu wizards with real working pagan sorcery that can actually rip your heart out. Hur hur.
The question then becomes "Which fits better with the overall tone of the films better?", not "Which one was more realistic?". It'd be like if in Lord of the Rings, flying saucers suddenly came and abducted Gandalf; both flying saucers and magic and equally unrealistic, but one of them fits in with the rest of the story better.
Also, going through the other posts here, I would not have expected a forum for Star Trek and Star Wars fans to hate geeks so much.
I guess you might not have noticed this, but the first three Indiana Jones movies were set in the 1930s, and featured elements of 1930s pop- strange cults, savage natives, exotic locales, lost historical treasures, the Nazis, all the elements of the pulp magazines. Crystal Skull was set in the 1950s, and featured elements of 1950s pop- the Red Menace, aliens, nuclear weaponry, and spies, the elements of the early Cold War. This was an explicit, deliberate decision by Lucas and Spielberg to work with Harrison Ford aging. Would you have preferred Indy suddenly aging twenty years between Last Crusade and a hypothetical Indy 4 without any acknowledgment of that gap in time? Or would you have preferred to pretend that the 1950s were exactly like the 1930s and so the tropes and elements of the earlier films would mesh well with the different setting? Even nuking the fridge can be argued to fit in well with the general lack of understanding about radiation at the time- witness Leslie Groves and Robert Oppenheimer inspecting the Trinity site with only plastic overshoes for protection, or the Ford Nucleon.
The Indiana Jones movies are very consciously period pieces adapting aspects of the pop-culture of the time. See the raft ride from the abandoned plane in Temple of Doom, the guys with swords out of nowhere in Raiders of the Lost Ark, or Indy stumbling into an impromptu meeting with Hitler and/or the Brotherhood of the Cruciform Sword in Last Crusade. None of those are realistic things, but they are part and parcel of the pop culture of the time. Oh wait, but those don't count for... some reason that boils down to personal taste. Personal taste is well and good. But when personal taste is propped up into a sham of universality, that is a problem.
Invited by the new age, the elegant Sailor Neptune!
I mean, how often am I to enter a game of riddles with the author, where they challenge me with some strange and confusing and distracting device, and I'm supposed to unravel it and go "I SEE WHAT YOU DID THERE" and take great personal satisfaction and pride in our mutual cleverness?
- The Handle, from the TVTropes Forums