Re: Indy, what was he really trying to obtain?
The Ark was a great MacGuffin, because it was always driving the story forward. And even though there was the danger of it falling into the hands of the "slime of humanity," we know they could never harness it, so it didn't really matter... so, yeah, it was a real MacGuffin. In the end, it just doesn't matter.
The Last Crusade? Well, Spielberg has stated, many times, that the "search for the Holy Grail, is the search for the father." And just like the Ark, the Nazis couldn't use it. So, once again, it was worthless. That's a MacGuffin, alright.
I think all the Indy flicks have great MacGuffins, but some are wasted as the motivation of the antagonist isn't the best. Sure, Mola Ram was an awesome villain, 'cause he spouted some great lines, but on the whole, I never believed he'd enslave the world. There was never any danger. (And from a the point of view of an RPF member, the Sankara Stones aren't the best.)
The same goes for the crystal skull. It never felt like Indy was in danger. Yes, he squirmed in his seat for a bit, but so did I... I did for different reasons, though. Having said that, technically, it is also a great MacGuffin; mainly 'cause, in the end, it just didn't matter. Sadly, that's 'cause nobody cared about anything in that show.