I wouldn't expect someone like Ang Lee or Lars Von Trier for the Die Hard series, but someone other than John Moore would have been nice. At least John McTiernan is a talented filmmaker with a solid repertoire of entertaining, quality action flicks (The aforementioned Die Hard, The Hunt for Red October, Die Hard With a Vengeance and The Thomas Crown Affair to name a few).
I'd say on a good day, McTiernan was as good an action director as there was out there; the original DH, Vengeance and Predator are proof of that. Plus those movies also showed he's good with an ensemble.
As I said before, you only have to contrast at how he handled the supporting casts or the setpieces in DH or WAV with how Wiseman handled that of 4.0. 4.0 had a decent enough plot and ideas but Wiseman didn't put them together the way McTiernan could have.
Even Harlin's 'slow-mo and, when in doubt, blow things up' mantra gave Die Harder a more distinctive feel than 4.0 had. I think that's why the Die Hard series deserves a grade A action director, as oppose to an anonymous hack like Moore.