My take on Indiana Jones IV is this: George Lucas is Indiana Jones and this is a Lucas film.
"I got a bad feeling about this"
In addition to the American Graffiti opening there is Star Wars all up in this mother. From the "bad feeling" line being dropped in a Indiana Jones film by Ford himself to echoes of The Trash Compactor scene when the group fell into the water when the temple steps retracted. The most awesome Star Wars scene of them all was The Empire Strikes Back one:
"Trust me"
Karen Allen as Marion Ravenwood is all sorts of awesome in this movie. In Empire, while piloting the Falcon, Harrison Ford pulled off all sorts of cool in the Millennium Falcon. In Indiana Jones IV, the Falcon is the amphibious jeep and Han Solo is played by Karen Allen. While Indiana and Mutt are going crazy over Marion's perhaps Crystal Skull fueled - crazed driving, she heads towards the cliff. Ravenwood is like "trust me"

drives over the cliff and lands on a tree branch which softly places the amphi-jeep into the river below. Marion accelerates over the branches and into the river causing the tree to snap back thus swatting the pursuing Irina Spalko gang.
And it don't stop because she won't stop - there is the cliche waterfalls scene. The catch here is there is not one waterfalls, not two waterfalls, but three waterfalls. Marion Ravenwood drives over and through them all.
The Droid Factory or Mutt Williams = C3PO
Unfortunately there is some negative aspects of the Star Wars influence. One of the criticisms of Attack Of The Clones is that C3PO was used way too much as comic relief which was most apparent in the Droid Factory sequence. In Indiana Jones IV, the Droid Factory sequence was (part of) the Jungle Chase. In one scene, Mutt straddles two jeeps driving parallel while fighting Irina Spalko. Somehow Mutt is ejected from the jeep into the trees above into a pack of monkeys. After observing the monkeys for a few moments, Mutt starts swinging from vine to vine and back into Marion's jeep.
When we first meet Mutt, he isn't C3PO at all. Mutt is Andrew Garcia from Godfather III, who to me was much worse of an actor and character then Sofia Coppolla's. Mutt's initial tough guy act just didn't come off to me. Although the subsequent beer snatching and motorcycle chase made up for it.
Prairie Dogs = Jawas in Podrace
Another lift from Star Wars is after Indiana escapes from the Russians (the first of many) and passes by a pack of CGI prairie dogs. We already seen one Prairie Dog in the opening and didn't need to see another gopher, much less 4 or 5 of them. This is Indiana Jones not Caddy Shack.
Other thoughts: In plenty of internet reviews there was mention of too much exposition. I found all the archaeological talk to be interesting and got the sense Lucas wanted to have Irina Spalko and Indiana Jones "help" one another because they shared the same interest in the Skulls in general. Cate Blanchett as Irina Spalko by the way kicked all sorts of ass. During the Jungle Chase she even demonstrated some Darth Maul style martial arts.
A few things did bother me: Indiana's removal from college. In Raiders and Last Crusade we were shown Indiana as professor with adoring female students. In Skull, Indiana was "let go" for allegedly being communist basically in front of his students. Later we see Indiana at home talking about the passing of Brody and Henry Sr. In the next scene we are introduced to Mutt who mentions his mom Marion. I guess this is to show we must lose old things so we can gain new things. There was way too many age-oriented comments by Mutt. Also, the fight between Indiana and the Russian was way too long. Lastly, Indiana should have used whip instead of the snake to get out of the quicksand.
Yeah Marion Ravenwood and Oxley were all sorts of awesome along with Indy.