I never saw Crystal Skull. But given how badly it was panned, even by a lot of pretty hard core Indy fans who had even given that abomination of a film that part III was (I can't even remember what it was called), I never had any desire to see it. I mean, if it was worse than III, I figured I would probably just walk out partway through, which I almost never do. That said, I still wouldn't mind eventually seeing it just for the sake of completeness, but just haven't gotten around to it.
I just recently saw Dial, and I thought it was pretty good. It can't touch the first two, but was still very enjoyable. Nice way to close out a legendary franchise.