I just wanna say, I'm reviewing this game, I finished this game 100% earlier today after a few days of play - all Chaos Emeralds, all unlockables, etc - aside from anything that might be unlocked from Tails/Knuckles alone runs - and seriously, if you can keep the secrets, do. As an old Sonic fan I cheered and hooted out loud at some of the things in this game - bosses, zone selection, etc, plus the gimmicks in the new versions of old zones. I honestly think it's worth going in not knowing.
If you're a hardcore fan who will relish the little references or even the bigger ones like zone selection, it's worth seeing it first time in your playthrough. Even saying [zone x] from [game y] is in it and in Act 2 it has the [thing] from [thing] in it is a massive downgrade on actually seeing it play out via the act transition or whatever.