At a panel at the Paris Games Week, Takashi Iizuka announced that players of Sonic Generations, coming in about a weeks time, will have access to the entire first game in the series as a bonus unlockable. He didn't give any indication as to how you'll go about unlocking the game, but I imagine that you'll have to beat time trials and jump through hoops (literally and figuratively) in a manner that won't be worth your time.
Because, seriously, if you're buying Sonic Generations in 2011, there's a good chance that you own a copy of Sonic the Hedgehog, either as a download or on one of the tens of compilations that have been released featuring the game.
If you honestly haven't played Sonic the Hedgehog since its release in 1991, congratulations; I'm hoping it isn't the ONLY unlock.
