Hey wow, somebody bumped an old thread. But, I've never seen it, so...
Indy4 takes the cheese cake for me, definitely. I'm not thinking so much of the wedding (the concept of which I still don't know how I feel about) but rather the dialogue when the heroes are sitting on the ruins of Akator, combined with the shamelessly recycled Grail theme. Yikes!
I think though, like all the Indy movies, Crystal Skull has a great last shot, with Harrison snatching the hat away. "Not so fast."
I think Temple's ending is cheesy as well, and I think Spielberg lingers on the kids too long and William's choice of music is a bit too bombastic, but the movie just feels like it earns the relentlessly happy ending after all the hell the characters have been through. It's kind of the same way I feel about A Christmas Carol. Scrooge's redemption is over-the-top, but as a story/movie it still works like gangbusters, especially when the preceding material was so dark (or at least it should be if the adaptation is worth a damn).