Yey, there’s an Android app called Gensoid (that you can download, Gensoid Lite is the free version without ability to save games) to install and play Sega Classic games on your Nexus One such as the Sonic Hedgehog (pictured above).
Here’s step by step instructions to install and play Sega Classic games on your Nexus One or any other Android phone:
1. Go to the Android Market and search/download Gensoid.
2. Next, download your favorite Sega ROM file off Google. ?For example, I did a search for “sega sonic rom” and found this site that has all the Sega Sonic ROMs. ?Just download the ROM file only, you don’t need an emulator as Gensoid is the emulator.
3. Next, connect your phone to your computer and copy the file ending in .SMD (these are the Sega ROM files) into your Nexus One’s SD card.
(e.g. Sonic 3 Sega ROM file)
4. Launch the Gensoid, browse your SD card and select the .SMD file.
5. That’s it, start playing Sega Classic games on your Nexus One or any other Android phone!
This made my day, I have never owned a Sega console but now I have it all on my Nexus One! ?WHOOHOO!