If Phil Spencer is a man of his word, he will re-establish the backwards compatibility program to add all the games from Original Xbox and Xbox 360 that they now have access to, having acquired Activision and all of its properties.
This is a substantial number of games.
When they ended the BC program, they claim they had exhausted the source of obtainable rights for additional games. That hurdle is gone now for a large number of games.
Phil has previously made claims that he is in favor of game preservation and that backwards compatibility is one way to achieve that.
To that end, Xbox should look to see which new games can be added to their library.
I have put together an incomplete list of games that were published by Activision or its subsidiaries for the Original Xbox and Xbox 360.
Some of these are obvious adds, since Microsoft will own absolutely every portion of the games involved (ex. Return to Castle Wolfenstein).
Others will still have licensing issues that can't be resolved, such as music and car model rights, and perhaps actor royalties.
But there would still be great value to the Xbox platform to add as many of the following games to backwards compatibility as they can.
007: Blood Stone
007: Legends
007: Quantum of Solace
4x4 Evo 2
50 Cent: Bulletproof
Aliens Versus Predator: Extinction
American Chopper
American Chopper 2: Full Throttle
Angry Birds Trilogy
Apache Air Assault
Bakugan: Battle Brawlers
Bakugan: Defenders of the Core
Band Hero
Barbie Horse Adventures: Wild Horse Rescue
Bass Pro Shops: Trophy Bass 2007
Bass Pro Shops: Trophy Hunter 2007
Battleship
Battlestar Galactica
Bee Movie Game
Bicycle Casino
Blade II
Blur
Bruce Lee: Quest of the Dragon
Buffy the Vampire Slayer: Chaos Bleeds
Cabela's Adventure Camp
Cabela's African Safari
Cabela's Big Game Hunter
Cabela's Big Game Hunter 2005 Adventures
Cabela's Big Game Hunter 2010
Cabela's Big Game Hunter 2012
Cabela's Big Game Hunter: Pro Hunts
Cabela's Dangerous Hunts
Cabela's Dangerous Hunts 2
Cabela's Dangerous Hunts 2009
Cabela's Dangerous Hunts 2011
Cabela's Deer Hunt: 2004 Season
Cabela's Deer Hunt: 2005 Season
Cabela's Hunting Expeditions
Cabela's Outdoor Adventures
Cabela's Outdoor Adventures 2009
Cabela's Trophy Bucks
Call of Duty 2: Big Red One
Call of Duty: Finest Hour
Chaotic: Shadow Warriors
Civil War: Secret Missions
Crash Bandicoot: The Wrath of Cortex
Crash Nitro Kart
Crash of the Titans
Crash Tag Team Racing
Crash Twinsanity
Crash: Mind over Mutant
Deadpool
Die Hard: Vendetta
Disney's Extreme Skate Adventure
DJ Hero
DreamWorks Shark Tale
Dreamworks Super Star Kartz
Enclave
Enemy Territory: Quake Wars
Eragon
Fallout: Brotherhood of Steel
Family Guy: Back to the Multiverse
Fantastic 4
Fast & Furious: Showdown
Fight Club
FlatOut
FlatOut 2
Futurama
Generator Rex: Agent of Providence
GoldenEye 007: Reloaded
Greg Hastings' Tournament Paintball
Greg Hastings' Tournament Paintball Max'd
Guitar Hero 5
Guitar Hero II
Guitar Hero III: Legends of Rock
Guitar Hero: World Tour
Gun
Hot Wheels: Beat That!
How to Train Your Dragon
Hulk
Hunter: The Reckoning - Redeemer
Ice Age 2: The Meltdown
Ice Age: Continental Drift - Arctic Games
Ice Age: Dawn of the Dinosaurs
James Cameron's Dark Angel
Judge Dredd: Dredd vs Death
Jurassic Park: Operation Genesis
Jurassic: The Hunted
Kelly Slater's Pro Surfer
Kung Fu Panda
Leisure Suit Larry: Magna Cum Laude
Lemony Snicket's A Series of Unfortunate Events
Little League World Series Baseball 2010
Mace Griffin: Bouny Hunter
Madagascar
Madagascar: Escape 2 Africa
Marvel Ultimate Alliance
Marvel Ultimate Alliance 2
Mat Hoffman's Pro BMX 2
Men of Valor
Metal Arms: Glitch in the System
MIB: Alien Crisis
Minority Report: Everybody Runs
Monster Garage
Monster Jam
MTV Pimp My Ride
MTX Mototrax
NASCAR The Game 2011
NASCAR: Unleashed
NPPL Championship Paintball 2009
Over the Hedge
Pitfall: The Lost Expedition
Predator: Concrete Jungle
Prototype
Prototype 2
Quake 4
Rally Fusion: Race of Champions
Rapala Pro Fishing
Rapala's Fishing Frenzy
Red Ninja: End of Honor
Return to Castle Wolfenstein: Tides of War
Robert Ludlum's The Bourne Conspiracy
Robots
Scarface: The World Is Yours
Secret Service
Shamu's Deep Sea Adventures
Shrek 2
Shrek Forever After: The Final Chapter
Shrek Smash N' Crash Racing
Shrek SuperSlam
Shrek the Third
Shrek-N-Roll
Singularity
Soldier of Fortune II: Double Helix
Soldier of Fortune: Payback
Spider-Man
Spider-Man 2
Spider-Man 3
Spider-Man: Edge of Time
Spider-Man: Friend or Foe
Spider-Man: Shattered Dimensions
Spider-Man: Web of Shadows
SpongeBob SquarePants: Plankton's Robotic Revenge
Spyro: A Hero's Tail
Starsky & Hutch
Street Hoops
SWAT: Global Strike Team
Teenage Mutant Ninja Turtles 2013
Teenage Mutant Ninja Turtles: Out of the Shadows
Tenchu: Return from Darkness
The Amazing Spider-Man
The Chronicles of Riddick: Escape from Butcher Bay
The History Channel: Battle for the Pacific
The History Channel: Civil War - A Nation Divided
The Hobbit
The Hustle: Detroit Streets
The Incredible Hulk: Ultimate Destruction
The Legend of Spyro: A New Beginning
The Legend of Spyro: Dawn of the Dragon (360)
The Lord of the Rings: The Fellowship of the Ring
The Simpsons: Hit & Run
The Simpsons: Road Rage
The Spiderwick Chronicles
The Thing
The Walking Dead: Survival Instinct
Tony Hawk's American Wasteland
Tony Hawk's Pro Skater 2x
Tony Hawk's Pro Skater 3
Tony Hawk's Pro Skater 4
Tony Hawk's Pro Skater HD
Tony Hawk's Project 8
Tony Hawk's Proving Ground
Tony Hawk's Underground
Tony Hawk's Underground 2
Tony Hawk: Ride
Tony Hawk: Shred
Transformers: Dark of the Moon
Transformers: Fall of Cybertron
Transformers: Revenge of the Fallen
Transformers: The Game
Transformers: War for Cybertron
True Crime: New York City
True Crime: Streets of LA
Ty3 the Tasmanian Tiger: Night of the Quinkan
Ultimate Spider-Man
Van Helsing
Vigilante 8: Arcade
Wakeboarding Unleashed
Wipeout 2
Wipeout 3
Wolfenstein (2009)
World Series of Poker
World Series of Poker 2008
World Series of Poker: Tournament of Champions
Wreckless: The Yakuza Missions
X-Men Origins: Wolverine
X-Men: Destiny
X-Men: Legends
X-Men: Legends II - Rise of Apocalypse
X-Men: Next Dimension
X-Men: The Official Game
X2: Wolverine's Revenge
I thought alphabetical order was the best choice, since it would be messy (and take a lot more time) to arrange them by platform, year, and publishing subsidiary.
Again, this isn't a complete list. Activision owned a LOT of stuff. But it's all I could find before I got sick of looking.
I have no idea why Shrek games were ever so popular