Alien Soldier, Dynamite Headdy, Gunstar Heroes, Streets of Rage, Phantasy Star, Sonic CD, Shining Force, Strider, Light Crusader, Snatcher.
These games/game series' need to be put on Steam.. Either because they're games everyone should play and/or they go for stupid prices on eBay now and aren't obtainable without forking over some large amounts of cash.
Sega always seem to forget these games that are, for the most part, constantly at the top of every fanmade Top 10 Mega Drive list. Hell they could branch out and sell some Saturn titles like Panzer Dragoon Saga or NIGHTS.
C'mon Sega, you've been beating around the bush forever, neglecting these games. Take a risk and put them up there, you'd probably be surprised.