Sonic 360 is one of the best fan games I've played in a long time - and this is just the first demo. There are several factors which make it really stand out. The first is the zoomed out camera. There's a nice wide-open view of Sonic, which makes long jumps look really cool. It really gives the impression of increased speed and agility. Combine this with the fact that the game is extraordinarily smooth and non-stick, and you have some great gameplay. The second is the range of moves. Sonic is equipped with the normal spin dash, and also a modified homing attack. You turn into a ball but don't home in on your enemies, but you stay in that ball as long as you are in the air. This allows for you to literally hop up and down on top of your enemies until they finally give in. It really adds that extra element of skill to the fan game. You also gain a new move every five levels, which is a perfect segue into the final great point of this game - the experience system. Sonic gains EXP every time he destroys an enemy, and even levels up just like in an RPG. As he levels up, attack and defense grow, and like I mentioned earlier, you gain new moves. It really is a genius system.
Now the game isn't exactly perfect, though close. There are some minor glitches, but hopefully these will be ironed out by Demo 2 or the final release. For now this game gets a 4/5.