Here's my list of 360 games that aren't backwards compatible.
Batman Arkham Asylum
Batman Arkham City
Battle Fantasia
Bionic Commando: Rearmed
Brothers: A Tale of Two Sons
Brütal Legend
Darkstalkers Resurrection
Dead Rising
Doritos: Dash of Destruction
Enchanted Arms
Enslaved: Odyssey to the West
Final Fantasy XI
Final Fantasy XIII
Gotham City Impostors
Guilty Gear XX Accent Core Plus
Legend of Korra
Magic the Gathering: Duels of the Planeswalkers
Marvel vs Capcom 2
Mortal Kombat vs D.C. Universe
Nier
Resonance of Fate
Samurai Shodown Sen
Sonic's Ultimate Genesis Collection
Soulcalibur IV
Soulcalibur V
Street Fighter III: Third Strike Online Edition
Super Puzzle Fighter II Turbo HD Remix
Super Time Force
Tales of Vesperia
Teenage Mutant Ninja Turtles 1989 Arcade
Ultimate Mortal Kombat 3
Worms
The bold ones on the list are the ones I would play if they had BC, but instead am leaving alone because my 360 sounds like it's having a heart attack whenever I play a game on it. This list also excludes Xbox Indies I have like Protect Me Knight and Cthulhu Saves the World, since they'll never be compatible anyway, which is a shame.
A good half of the other games I own are backwards compatible though. That's nothing to sneeze at.
EDIT: oh, turns out I was looking at the first page, where everyone was talking about their collections, and now I'm talking over actual recent news. My bad.