Well, since everyone is talking about this game. I will talk too. I finished a little ago everything, and now I can proper talk about.
And is AWESOME! Have everything I wanted in a Sonic game, I can't ask for more. I even dropped a tear of joy when played! Let's first focus on the good things:
The game is nostalgic, of course, but the game don't rely only on nostalgia, no sir, the game can hold for himself pretty well. Each stage only have some landmarks from the past, but most part of then are completely original. You have a lot of paths to follow in the stages, and each path can take a different skill level.
Classic Sonic have, finally, his physics back. This is what Sonic 4 should was to be made, with the right physics back! Classic Sonic have a lot of plataforming but don't be fooled, the speed is still there and go strong, like Sonic 3.
Modern Sonic is exact his Color's counterpart.... what is a REALLY good thing, because his stages are not only BOOST BOOST and BOOST SOME MORE. Like Color's, he have a lot of plataforming as well and different paths to take in a stage.
The Rival battles are EPIC, seriously, since a LONG time I don't enjoy a boss battle in a Sonic game, but here, they are ALL fun and give you a epic vibe, even they introductions' pass this. The Major Boss Battles too are all Epic and such, but the one that chill my spine is the boss battle of the Second Era... Dear God, this was so much epicenes for my little heart! I can't tell spoilers, but anyone that really played the Adventure games will love it!
The music, well, what I can say about the music that anyone else as said? Is FURDELICIOUS. Both classic and modern remixes are very well made and nostalgic, and some I now like more than the original! (Like, City Escape in the Classic Remix!)
Classic doesn't play EXACTLY like his Genesis version. The rolling kinda suck, the spin dash are super OVERPOWERED. You can make an spin dash anywhere with no punishiment or whatso. Now the game needs a lot more precision in the jumps than before, and the mommentium are a bit weird. Those things can or not be considerated "bad things" but cuts a bit of the enjoyment of the game.
Modern Sonic rely most on reflexes, and can be quite frustrating when you miss. Is hard you die when you miss a path, but will make you end up in a less fun path of the stage. This is normal on Sonic games but sometimes you end up missing just for some mileseconds.
Some challenges are a pain in the ass. Not because they are hard, but because they are annoying.
The Story is a big letdown a bit, but is just a excuse to join Sonic with his Classic self, so, not that big problem.
And, a big problem in the last boss fight. I don't gonna spoil but, Sonic friends maybe have to keep their mount's shut for a second, please! XD.
Overall, The challenges are fun, the stages are fun, the rivals are fun, the bosses are fun, even the DLC Casino Night Zone are fun! This game is pure funess!
If you are a Sonic fan, buy it! If not, BUY IT TOO, this game is good for anyone, not only for Sonic fans.