UPDATE: I've finally, FINALLY gotten this achievement! WOW on a carousel! This was was a NIGHTMARE to get but after getting so flustered and angry at times over it, I finally got the patience to come back and give it another go.
Needless to say, I've finally gotten this achievement and now I can FINALLY let this awesome game rest in peace with all of it's achievements unlocked. It is now my second game that I've successfully platinum-ed.
Granted, I do stand by certain aspects of my previous post with the final boss being near-absolute bullshit that dogs an otherwise great game. The controls are a pain, you have to be lucky to get the rings to avoid dying from rings running out, and the third part where he fires a barrage of rockets at you is what got me so many times, the fourth well.....you decide. However, with "Can't Touch This", I can now boast of 1000-ing this game and now the points I said I docked from this game's rating are restored and I overall give SG a 94 out of 100.
It's a huge pain to get. It took me numerous tries but apart from this crapfest of a boss fight, "Sonic Generations" is my favorite Sonic game since the Sega Genesis days.
Good luck guys.