Really difficult old game could be released in 2012 to delight old people.
PEGI has rated Alex Kidd in Miracle World for Xbox 360, suggesting an eventual release for the SEGA Master System classic.
Spotted by Siliconera, the European ratings board also took a glance at Super Hang-On, Golden Axe, Golden Axe 3, Streets of Rage, and Streets of Rage 3. I'd imagine Golden Axe and Streets of Rage will be the Mega Drive/Genesis versions of the games, rather than their inferior (but still quite cute) Master System counterparts.
The Golden Axe and Streets of Rage games are also available as part of the SEGA Mega Drive Ultimate Collection - which picked up a respectable 8/10 in its review - on Xbox 360 and PlayStation 3.
PEGI also rated Wonder Boy in Monster Land, Wonder Boy in Monster World, and Monster World IV. The last game has never been made available in English before.
Alex Kidd in Miracle World was actually built into Master System II machines, and was the first game I ever owned. It caused me many sleepless nights because I remember it being painfully difficult, and I never completed it.
If you're too young to remember Alex Kidd in Miracle World (or you had a NES), here's a little audiovisual taste: