Imaro
Legend
Depending on which story you read both [-]Gawain[/-] Percival and Galahad were good enough to sit upon The Siege Perilous (it's a magic chair) and thus initiate the Grail Quest, and one or the other actually do complete the quest and recover the Grail.
Were a few of the Knights rather despicable? Yes, my above post lists some of the worst offenders (Bedivere, Kay, and Tristan stand out). But the rest were either decent to middling good with some truly breakout "Chivalric Knights".
Why? Well... see... the stories were written and told over several hundred years. The earlier Knights trended toward the flawed, the later knights stood out as "the best" since they were written after Chivalric Romance swept the arts.
I'm not understanding the point of this post? Those "knights" you are speaking of outside Galahad (and possibly Percival) are not paladins to those who advocate for the LG paladin... they are cavaliers, or fighters with a code/kit/noble background/etc. as to the why... it's irrelevant to the discussion the fact of the matter is that Galahad is held above a regular knight and this was the archetype the LG paladin was supposed to embody... the epitome of good.