"Sonic Mega Collection Plus is an update of Sonic Mega Collection for the PlayStation 2 and Xbox consoles. A PC version was also released in Europe and North America. This edition includes the addition of six Game Gear games, the two games that were included in the Japanese version of Sonic Mega Collection (The Ooze and Comix Zone), new artwork and movies, a new in-game menu, and a mid-game saving feature. It is, however, missing six Sonic Game Gear games that were included (along with the six included in this collection) in Sonic Adventure DX: Director's Cut, but they would later appear in Sonic Gems Collection. In addition, only the final Japanese revision of the original Sonic the Hedgehog is included. The PC version was released on March 9, 2007 in North America. The localization for this version of the game is the European Localization. The original packaging says CD-ROM, but it is in fact a DVD-ROM; it will not play in a CD-ROM-only drive. The European packaging is correctly labelled. The PC version also uses the PAL-50 versions of the Mega Drive games instead of the NTSC-60 ones, and the game therefore runs at the slower 50Hz. The PC version was re-released in 2009 as part of Sonic PC Collection."
Source: Wikipedia, "Sonic_Mega_Collection," available under the CC-BY-SA License.