Sega's promotional event Make War Not Love offers 2 free Mega CD games (Revenge of Shinobi and Streets of Rage 2) when you sign up. Plus you will have the chance to get daily prizes.
1. Sign up with your steam account on their website.
2. Confirm your email address.
3. Games should be in your Steam account over the next 24hrs.
4. The game installs as Sega Mega Drive And Genesis classics and each of the 2 games is a DLC.