Finished it last night. It really is a great game - really enjoyed it. Got my Super Sonic unlock but it costs a lot of skill points to use. I'm now making way through all the challenges (there are TONS), trying to get S Ranks and get all the skill unlocks - there is a Skill system. You unlock skills and can improve either modern or classic sonic and there are a lot of skills to unlock. (I haven't even unlocked half)
The game really does have a lot of replay value. I must say that I enjoyed some of the modern Sonic levels over the classic 2D levels (gasp!) - it's actually a lot of fun once you get used to it. I highly recommend this game be played with some sort of controller (Xbox 360 controller works fine). Playing with a keyboard is fine, but the controls are much harder to learn/get used to.
The game also takes the piss out of itself sometimes especially when younger Sonic, Tails and Robotnik meet the modern versions of themselves.
Younger Tails to Older Tails: "He collected how many rings? Wow! Where does he store all of them?"
Older Tails to Younger Tails: "You know... I've never bothered to ask..."
The babbling between old and new Robotnik is also very entertaining. "Do we ever catch that Hedgehog?....No."
Here is a list of all the playable stages and which Sonic game it comes from :
Green Hill - Sonic the Hedgehog
Chemical Plant - Sonic the Hedgehog 2
Sky Sanctuary - Sonic 3 & Knuckles
Speed Highway - Sonic Adventure
City Escape - Sonic Adventure 2
Seaside Hill - Sonic Heroes
Crisis City - Sonic the Hedgehog (2006)
Rooftop Run - Sonic Unleashed
Planet Wisp - Sonic Colors
