I'm not sure exactly what to call this.  It seems I may have heard someone refer to it as incidence rate.  What I am looking for is a UI that will analyse a game, compare it to the moves suggested by an engine, and then tell me the % match.

Is there a way to automatically do this - basically tell me how many moves were the best move according to the engine?

I guess I could do a blundercheck with a threshold of 0, but that seems clumsy.

I'm unaware of any software that'll give the percentage like that, but you can use Crafty's annotate feature to go through a pgn and add comments whenever your move is worse than the engine's by a certain score.  You set the score yourself, so for example, you could have Crafty give you comments on any of your moves that lose more than 1 point (a pawn), or if you want more positional comments, choose a value like 0.5.

If you haven't heard of crafty, search for craftychess.  It's free.

I only know of two programs that do this. One is a private program named Batch Analyzer, which I've only heard about. The other is ChessAnalyse, which is commercial, but you can download a trial version in the Chess.com download area.