From all film versions I found Excalibur the only one worth watching, it's very very 80s and over the top, but has the atmosphere just right and plot more or less right. Of course there are many variations on the actual myth, pre-medieval, Romance, 19th century Tennyson et all, so there are tons of variations on the plot. But of course, nothing even vaguely reminiscent to what we are watching now!