This really came out of nowhere. It's a collection of Genesis titles made by Sega, including Streets of Rage series, all/most of the Genny Sonic games, Phantasy Star series, Golden Axe series, Altered Beast, some Shining titles, and more obscure stuff like Bonanza Bros. and Alien Storm totaling about 40 games in all. BUT it also has nine unlockable games that you open up through achievements in the available-from-the-start games that includes arcade versions of Fantasy Zone, Shinobi, Space Harrier and others along with the Master System versions of Golden Axe Warrior and Phantasy Star 1.
For the most part the games are straight ports, although there is a smoothing filter [which is cool or an abomination, depending on who you are], 16:9 support [which is basically a stretched out 4:3 screen, but look okay in action] and original 4:3, as well as a save anywhere function for all games. And it only costs $30.
Well worth it for fans of 16-bit gaming.
