Xbox Live is having a sale on all of the good Sega games including all of the Sonic the Hedgehog games.  Sonic and Friends are discounted below:

Sonic The Hedgehog 4 – Episode 1 — 33% Off 800 MSP
Sonic Adventure — 50% Off 400 MSP
Sonic The Hedgehog 3 — 50% Off 200 MSP
Sonic The Hedgehog 2 — 50% Off 200 MSP
Sonic The Hedgehog — 50% Off 200 MSP
Sonic & Knuckles — 50% Off 120 MSP
Sonic The Hedgehog 4 Episode 1 Select Avatar Items — 50% Off
Phantasy Star II — 50% 200 MSP
Ecco the Dolphin — 50% 200 MSP
Happy Tree Friends – False Alarm — 50% 400 MSP

Sega Arcade Deals
Crazy Taxi — 50% Off 400 MSP
After Burner Climax — 50% Off 400 MSP
OutRun Online Arcade — 50% 400 MSP
Cyber Troopers Virtual ON OT — 50% 600 MSP
Streets of Rage 2 — 50% 200 MSP
Gunstar Heroes — 50% 200 MSP
Golden Axe — 50% 200 MSP
Altered Beast — 50% 200 MSP
Comix Zone — 50% 200 MSP
Shinobi — 50% 200 MSP