I actually heard a conference paper a few years ago on the subject of why H1 was a terrible king :) I think the presenter was just being contrary and slightly silly (very senior scholar with a good sense of humor; he could get away with it), but it was entertaining all the same. I'm agreeing with your assessment that H1 was a Good King TM in general, though, because he had to overcome a lot of early rebellions in order to do the things he did.

I also think that Edward the Confessor should at least be a + because even though he screwed up his succession (and mother, trial by ordeal, what? missed that one!) he was mostly a very good king during a rough time.

Oh, and H6 lost the Hundred Years War, too, but there can't be any more minuses than he already has! I'll balance that out with 'the poor guy became king when he was a baby.'