Here is the list with IMDB links...
ARGO - Chris Terrio
BEASTS OF THE SOUTHERN WILD - Lucy Alibar, Benh Zeitlin
LIFE OF PI - David Magee
LINCOLN - Tony Kushner
SILVER LININGS PLAYBOOK - David O. Russell
A little more detail and the trickiness involved with the adaptation...
Argo is adapted from an article but based on true events - events recent enough for lots of people to remember perhaps.
Lincoln is from a book but based, of course, on historical events - but events so famous that everyone knows about it (no chance to sneak in a twist at the end here, or is there?)
Life of Pi is from a novel about a boy in a lifeboat with only a tiger for company - not much chance for dialogue perhaps.
Beasts of the Southern Wild is set in a flooding swamp but is based on a one act stage play! Is there enough material to work with for a feature film? (Cheeky personal link here as this is the first feature from producer Josh Penn who I met in Cannes in 2011).
Silver Linings Playbook was adapted from a novel, whose message was that love isn't like a Hollywood film, so a big fat self-contradiction there then.
What I like about the solution (in fantastically general terms) that all these writers used was that they weren't afraid to do these adaptations in a direct and simple manner. Now, just to be clear, I've only done a very small amount of adaptations but I know its tough. I'm not saying these are easy to do at all.
However sometimes, as writers, we want our adaptations to be as original as the source material, yet these film don't rely on gimmicks or super-complex structural solutions. Instead they aren't afraid to tell stories in a linear order, to use narration / voice overs and to employ classic story structures. Some writing critics may frown upon some of these techniques and call them simplistic. I disagree. Here they are powerfully used. They let the original material shine through. They are transparent techniques.
This is why, I believe, they are all good adaptations. They put the material at the heart.