Aaah, the classics. It brings a nostalgic tear to your eye doesn't it? *sniff*
This is a solid collection containing all the classics - Sonic the Hedgehog, Sonic 2, Sonic 3, Sonic and Knuckles, etc., and some games that will shock you, games like cult classic Ristar, and Comix Zone.
Some games are weak, however, like the Game Gear racing title Sonic Drift, and Dr. Robotnik's Mean Bean Machine - the name alone tells you to stay away.
This does not matter however, and if you no longer own a Mega Drive (or Genesis for you Yanks), this is a must-buy.
And if you don't like Sonic... you can go to hell.