The Master System version of Sonic the Hedgehog 2 was never released in North America (only the inferior Game Gear version made it there), so its appearance on the ESRB database (which pretty much guarantees a Virtual Console release) is a little bit of history in the making. A very little bit, mind, because the differences between the 8-bit Sonic 2s are trivial, to say the least.
We never played either iteration, so are unqualified to comment on the game's quality, but Wikipedia informs us that this was Tails' debut appearance, which also means this game marks the start of Sonic having friends. Man, look how that turned out.
[Via Go Nintendo]