Info from sega's site, crazily no Sonic CD
To be this good take AGES, to be this good takes SEGA!
Re-live old memories and create new ones with this exceptional all-in-one package of over 40 classic titles from the golden era of the SEGA MEGA DRIVE! The most complete collection to date contains a huge range of top-quality, iconic moments in gaming history. You can now experience these fantastic single and multi-player titles in enhanced HD graphics for ultimate involvement!
Exclusive Unlockable Content: Unlock arcade games and interviews with the original game developers as you earn Achievements on the Xbox 360® and Trophies on the PLAYSTATION®3.
Hi-definition Upgrade: All titles included in the collection have been converted to vivid hi-def (720p) visuals to truly enhance that classic 2D experience!
Multi-player Option: Two players can now enjoy select titles together on the same console at home.
The Most Comprehensive Collection of Classic SEGA Titles:
Alex Kidd in the Enchanted Castle
Decap Attack starring Chuck D. Head
Dr. Robotnik's MBM
Ecco the Dolphin
Ecco II: The Tides of Time
Golden Axe I
Golden Axe II
Golden Axe III
Phantasy Star II
Phantasy Star III: Generations of Doom
Phantasy Star IV: The End of the Millennium
Shining in the Darkness
Shining Force 2
Shinobi III: Return of the Ninja Master
Sonic 3D Blast
Sonic and Knuckles
Sonic The Hedgehog
Sonic The Hedgehog 2
Sonic The Hedgehog 3
Streets of Rage
Streets of Rage 2
Streets of Rage 3
Super Thunder Blade