The Mega Sonic Collection (or whatever it's called) was a perfect fit for Gamecube. First off, the Sonic series is very popular on Gamecube, probably most popular. And a lot of the material (i'd assume the game ROMs) was the same from Sonic Jam on Saturn. i doubt we'll be seeing more Sega collection on GC though. As dafunkk12 said, they're bringing some of their older games to PS2, likely in part because of the larger userbase.