The Progression of Arthurian Champions...
The original trio: Arthur, Cai and Bedwyr - the Heroes of the Welsh Corpus. Standing for: Supreme Warrior Prowess in this world and the supernatural Otherworld, Proto-Nationalistic Resilience against foreign encroachment, and the Bardic Tradition.
Sir Gawain, the First Exemplar of Courtliness and (Secular) Chivalry - The 1st Hero the non-Welsh writers latched on to project an ideal model of the emergent Code of Chivalry and Courtliness. A bit rough around the edges as he combines traits of old and new modes such as supernatural abilities, combative knighthood, heroic lineages and blood ties alongside refined manners and the championing of ladies.
Sir Lancelot and Sir Tristan, The Knights of Love - Building on the ground tread by Gawain, here we have two figures whose mode of heroism is expressed though their steadfast pursuit of their respective Beloveds, despite the taboos inherent in such. As Medieval Romance holds that emotions, and in particular Love, are supreme forces that affect the heart and body, these two men are thus elevated above all other warriors, in both physical prowess and nobility, thanks in part to the great passions they harbour.
Sir Percival, Sir Bors and Sir Galahad, the Spiritual Trio - As the Legends reach the apex of its religionization, there comes an awareness that the previous models do not fit the highest theoretical standards in accordance with the faith, of which is the rejection of the worldly and material, with a particular bent towards sexual matters. Thus, out of the deconstruction of the previous characters (namely, Lancelot and Gawain), the characters of Percival and Galahad were put forward, with the third figure of Bors included to fulfill a thematic trinity of knights.
Sir Segurant - A small retrograde movement away from the progressions of Lancelot (Romantic Love) and Galahad (Spirituality), a sort-of course correction towards basic chivalry and less high-minded pursuits, such as monster-slaying. Also found is the undercurrent of the Prior Generation's greatness, as members of the Knights of Uther Pendragon's Round Table (which includes Segurant's family) are shown defeating the Knights of Arthur's Table.
And with that, I guess the question now becomes "What about now? Where next?". Hard to say, though there's certain themes I've noticed that hopefuls are cultivating in Arthuriana. There's Feminism (Guinevere and the Ladies as the hero(ine) and as warriors), Art/Brains-over-Brawn/Magic (Merlin and other magic users as the hero), Counter-Narratives (Traditional villains like Morgan and Mordred as the hero, Paganism-vs-Christianity) and Non-Conforming Identities (Any, but Galehaut and Lancelot come to mind)