Henry VI's reputation was summed up by one of my lecturers:
"In 1453, when he received news of Castillon, Henry VI fell into a catatonic state. This was a sizeable setback for the realm...[discussion of the regency/protectorate]... in December 1454, a disaster of unprecedented proportion hit England. Henry VI recovered."
That says a lot. If you're a better king while you're a vegetable than you are when you're able to rule, then you're obviously not great on the 'ruling'. Shakespeare's history may not always be the most accurate, but Henry, his wife and his advisers did "Lose France, and made his England bleed."
Edward IV did incredibly well to win his throne back in 1471, and must be applauded for it. That being said, he never should have lost it in the first place, and only did so due to some incredibly stupid decisions. Richard managed to reignite a conflict that had been dead for over a decade, essentially driving most of Edward IV's surviving partisans into the arms of Henry Tudor. Henry IV saw all sorts of instability, and effectively lost Wales for several years. Edward V ruled far too sgort a time to be worthy of being judged.
That leaves Henry V. I can't help thinking that, had he survived another twenty or thirty years, he might have lived long enough to become the villain. Look at Edward III in 1359, and then in 1377, for what I'm imagining might have happened if Henry had lived longer. As it is, he didn't, so I shan't judge him on possible ATL failures.
Henry V best. Henry VI worst.