The 6th gen is the 128-bit era, this is the time of the ps2, xbox, game cube and sega dreamcast, there was apperintly another console called the XaviXPort but i never heard of it. This era ended arounf 2005 when the xbox 360 came out.
This is what I consider to be the last Sonic game. Sonic Adventure 2 was okay, and then the Sonic Franchise went down to hell.
THE MESSIAH !
You're right, after SA2, Sonic went out... very fast.
SA2 battle is better, playable to the gamecube