Here's my brief history of Sonic the Hedgehog:
Sonic 1: Ugh, this is better than Super Mario World...HOW?!?
Sonic 2: OK, a little bit improved, and Tails is awesome! Love the pinball stages, they should make a whole game out of that.
Sonic Spinball: Well look at that!
Sonic CD: Hey where'd Tails go? And thanks Sonic, for making other comanies develop crappy mascot platformers who are rodents with attitude. I skipped out on a lot of 16-bit platforming because of you.
Sonic 3: OK, this one is pretty decent.
Sonic 3-D Blast: Hey, it's like a cross between two games I like: Flicky and Marble Madness. So why all the hate?
Sonic Adventure: This was pretty good for it's time.
Sonic Adventure 2: I'd like it a lot better if the camera angles weren't so awful near the end.
Sonic Heroes: Lots of good ideas, but buggy as hell.
Shadow and Sonic 2006: I think I'll skip out on Sonic games from now on.
Sonic Generations: Pretty good, but I only played it because I reviewed it.
Sonic & Sega Racing games: Hey, they outperformed Mario Kart in some areas. And any game with Ulala can't be all bad.
I'd like to play games like Sonic Colors and Sonic Lost World (especially the Yoshi and Zelda DLC), but I'll wait for the price to go down on those.
Sonic Cartoons:
Sonic Saturday Morning: Eh, it's OK, don't know why everyone likes it so much.
Sonic Weekday: So bad it's good.
Sonic Underground: Ahhhh! My eyes, they burn!
Sonic X: Definltely the best one.
Sonic Boom: BWUA HA HA HA! Look at Knuckles!
Wish I could say more, but I have to go to work.