I think the last one is the weakest, only because the plot was too "grand" for it to really fit into McClane pretty much just been the everyman in the wrong place at the wrong time. But here he gets involved in a national incident that'd likely have pretty devastating effects on things? It just really didn't seem to fit into the "Die Hard Universe."
I still enjoyed though but it had it's problems, also being PG-13 harmed it and the R-Rated/"Unrated" cut doesn't improve things. Just over LFaDH I'd put Die Hard 2 which also has some problems. Die Hard itself is obviously an endless classic and Vengeance is just pure awesome.