Originally Posted by
FieryReign
I wouldn't bother with Outrun, Space Harrier, or Afterburner. They are pretty shoddy ports, the SMS simply wasn't capable of duplicating the arcade games. If you have a Dreamcast or GBA, they can be found on Shenmue and Sega Arcade Gallery. Since you're playing on a Genesis, even that version of Outrun is much better. Same with Phantasy Star and the various compilations.
I would recommend Spellcaster, a unique hybrid of adventure game and sidescroller. Wonderboy 3-Dragons Trap and Alex Kidd in Shinobi World are a couple more good ones. Kensieden is a hack n slasher with nice graphics but it's ridiculously hard.