I actually liked Crystal Skull better than Temple of Doom (though they are both by far, the two weakest films of the four). Shia Lebouef was a very poor casting choice for the role of Indy's son and weighed the movie down, but apart from that, other aspects of the film IMHO captured the cold war atmosphere and intrigue of the 50s...
TOD was 2nd best. Crystal Skull was not good. Last Crusade was not that great. Not a huge special effects fan, but Last Crusade was probably the worst special effects I’ve ever seen.
Plus, watching Last Crusade is probably illegal in the current climate.