I’ll be forever stuck on the (book) Mists of Avalon as my bar for all things King Arthur, so probably anything will pale in comparison! It’s a multi-season series, so it’s REALLY taking it’s time getting going. Eva Green is quite good as the evil Morgan, and Joseph Fiennes is only a little bit heavy handed as Merlin. However, could they have found a more annoying actor to play Arthur? He’s fine when he’s supposed to be Arthur the petulant boy, but supposedly he’s growing into being a king, and he just ISN’T selling it. And his ears stick out. Also, Guinevere is too blond and annoying — okay, that’s her job, I suppose! Sadly, My Boyfriend(TM) James Purefoy doesn’t stick around through the whole series, but he eats the scenery in the ones he is in! The costumes are fine, nothing terrible — your standard proto-medieval gear.
I grew up devouring Mists of Avalon every few years. My mother should definitely have been monitoring my reading more closely. Recently I picked up Sword at Sunset which may have just MoA as my favorite rendering of the Arthurian legend. It takes the 6th century very seriously, and while written by a woman, it’s the closest I’ll ever get to understanding the mind of a man.