King Lear has generated more movie versions than most Shakespeare plays, and it's not hard to see why. The dialog (particular in the hands of first-rate actors) is direct and powerful, and there are lots of scenes that are quite cinematic in nature. This one, from 2008, has the look and feel of a live-stage production (which it was) but just without the theater audience. The sets are quite simple and spare, so it doesn't have the advantages of bigger-budget movie Shakespeares like Branagh's Henry V or Much Ado About Nothing, Taymor's The Tempest, or Zeffirelli's Romeo and Juliet.
But the compensating advantage is that without lavish sets and scenery you can concentrate on the actors and their roles. Ian McKellen leads this cast, justifiably so, and turns in a Lear that sticks in the memory. It's complex, nuanced, and entirely believable as the journey of a man who painfully acquires self-knowledge very late in life. I've seen very fine versions of Lear on live stage including Christopher Plummer, Brian Bedford, William Hutt, and even Peter Ustinov, but McKellen's version really stands with the best.
The rest of the cast is just fine. I want to mention particularly Romola Garai: her portrayal of Cordelia is not the shy child that we often get; instead, hers is a more forceful and aware woman, still young but well beyond her insecure teenage years. She comes across as someone we would really like to know better. Garai's version is perhaps the most interesting one I've seen. So many of Shakespeare's plays have young heroines that we, the audience, so easily fall in love with and desperately want to see succeed -- Juliet, Rosalind, Viola, Innogen, Miranda -- but I think Cordelia heads them all. Even though she is not on stage all that much, once we meet her in Act One Scene One she is constantly in the back of our minds, and when she finally returns to the action near the end it is like a fresh breeze. At last! something good is happening again! Because in the meantime, with Lear, Goneril and Regan, Edmund, Edgar, Kent, and Gloucester, we've been put through the wringer for quite a long stretch.
King Lear is Shakespeare's deep look into the worst, and best, of human beings pushed to their extremes. No single version of Lear does complete justice to everything that's in it, but this version deserves to be in the list.