Sonic Jam
"Sonic Jam" is a compilation which contains the four main "Sonic the Hedgehog" games released on the Sega Genesis: "Sonic the Hedgehog", "Sonic the Hedgehog 2", "Sonic the Hedgehog 3", and "Sonic & Knuckles". Unlike future "Sonic" collections, "Sonic Jam" does not use a Genesis emulator; the games are proper ports, and all are nearly identical to the original Sega Genesis releases, with the exception of minor bug fixes. "Sonic Jam" emulates "Sonic & Knuckles" "lock-on technology"—a special feature that allows the player to merge elements of "Sonic & Knuckles" into previous games, resulting in changes to the level design as well as the choice to play as Knuckles the Echidna in "Sonic the Hedgehog 2" and Tails in "Sonic & Knuckles".
Sonic Gems Collection
Developer Sonic Team conceived the compilation to introduce younger players to older "Sonic" games. One game they wished to include, "SegaSonic the Hedgehog", was excluded due to emulation difficulties. Sega released "Gems Collection" for the GameCube and PlayStation 2 in August 2005. Reviews were mixed or average; critics were divided over whether the package would satisfy players. They preferred "Sonic CD" and "Vectorman", but found "Sonic the Fighters" and "Sonic R" mediocre, and disliked the Game Gear games. Some were disappointed by the absence of the "Streets of Rage" games in the American version and other "Sonic" games like "Knuckles' Chaotix" and "Sonic the Hedgehog Pocket Adventure".