The ESRB has been quite specific, calling the game "Sonic the Hedgehog on Master System" in its rating, so you can be 100% sure that it is coming to the Virtual Console sometime soon. The Master System version of Sonic the Hedgehog looks similar to the Mega Drive / Genesis game, however, the levels are completely different, so if you enjoyed the original game you will probably like this one as well. This was the last game released for the Master System in the USA also, Sega's swan song to North America!
The ESRB has also rated Splatterhouse 2, the Mega Drive / Genesis sequel to the original Splatterhouse, which is on VC. This game was also previously rated by the OFLC, and Japan got it this month, so it is not unreasonable to expect it very soon.