This is an interesting thread.
Well, ya see... it's not that I didn't like the scene with the ants... the fact is that... well, I think it is the worst scene of the entire saga...
It surely is the big let-down of the movie. And I'm saying this not because it looked CGI fake or whatever... I absolutely don't mind CGI (on the contrary... I'm almost getting sick of people blaming it, every single time, and always without minimally explaining a VALID motivation for that).
The problems with the ants sequence are various... the scene is TOTALLY UNORIGINAL and, on the other hand, it's WAY TOO GROTESQUE AND DISGUSTING for an Indiana Jones movie, in my opinion. All of the previous Indy movies were generally lighthearted, some kind of "innocent". By having inserted the ants sequence, which features two of the most brutally horrible death scenes I've ever seen in a movie, you have just somehow changed the global feeling. Even the sacrifice scene in "Temple of Doom" was less disturbing than the scene with the ants in "Indiana Jones 4". FAR LESS disturbing... and I'm writing from Italy, where censorship on movie scenes doesn't exist, so I've always seen the uncensored sacrifice, ever since I was a little boy.
Now, I just wanted to write a few lines on originality... like there was the need to...
Pass that the ants may be a citation of great B-movies from the past, but... damn... we have already had insects in "Temple of Doom"... LOTS OF INSECTS... TONS OF INSECTS...
Not to mention that the scene in "Kingdom of the Crystal Skull" is only a mere copy of an analogue scene from Stephen Sommer's "The Mummy".
No, definitely... the film is set in the Amazons, they should have used piranhas, as deckard24 suggested. They would have been:
1) MORE ORIGINAL
2) MUCH BETTER
3) WAY MORE SPECTACULAR
Now, imagine a scene in which thousands of little piranha-monsters jump out of the water, obsessively trying to reach our heroes... imagine all of the splashes in the water... imagine all of the reflexes of the light on the little shiny bodies of the piranhas... THAT WOULD HAVE BEEN A GOOD SCENE. MUCH MORE ADVENTUROUS, SPECTACULAR, ORIGINAL AND SUGGESTIVE.
After all, I think the ants sequence was bad. REALLY BAD. And out of place.