For me, Lancelot was always the greatest of knights- not only because of his near-umatched prowess on the field, but also because he was flawed. I would put Tristram second; in reading his exploits I always felt he was second to none, save Lancelot. Gawaine third, his strength waxed to that of three men between nine and noon- coupled with his prowess, he would've been a most formidable opponent. Also, he too was flawed, by his jealousy of Lancelot. I'd go with Perceval fouth as he was a devout knight and one of a select few worthy of espying the Holy Grail. 5th, I would put forth Gawaine's youngest brother, Gareth, over Ywain...I feel his exploits should have won him more renown, not to mention, his ability to control his temper, as the constant bullying from Sir Kay over his pale white hands would've been enough to go to fisticuffs for most other men. I never liked Galahad...he never seemed real to me...as such, he doesn't make my top 5 list.
I've read Malory's Le Morte d'Arthur; another good read (and different take on the Arthurian Legend) is Once and Future King, by T.H. White. I liked White's rendition because it dealt with Arthur the boy, then as a man before he took the crown; it paints a very human picture of him that I especially liked.
Das Bill, I've always taken it to mean that the shield and surcoat matched in solid color, but mail was mail was mail and any coloring it might've gotten would've been through rust I'd imagine; just my op on it.