It's not a fantastic game, but it's okay.
I wasn't expecting much but when I got it on Christmas Day, I was pleasantly surprised. Yes, I did have a brief look at the game when my friend bought it but once I had the game for myself I got the full experience. I would say that, having played this game properly, it's not a bad game at all. There's nothing really fascinating here, but it's an okay game nonetheless.
The storyline is a little corny, no doubt about that and it isn't the best storyline either; Eggman has a camera and can turn anything into a card simply by taking a picture of it. He has already turned Tails, Amy and the Master Emerald into cards and it's up to Sonic to rescue Tails and Amy, while Knuckles goes after the Master Emerald. Shadow and Silver are also in this game, and to my knowledge (I haven't played either of their stories yet), both are after Eggman.
The four Rivals; Sonic, Shadow, Knuckles and Silver race against each other quite simply. The story mode can be a little difficult for those new to the game and frustrating sometimes, especially when racing against Silver, who can mess up your controls (not literally) with his special attack. Despite that, it can be good fun if you are looking for a challenge or if you just love Sonic games. There is even an inclusion of boss battles, which in my personal view, are slightly easier than the races themselves and in most cases, you have to beat the boss before your Rival does by scoring more hits.
As well as story mode, there is an inclusion of a challenge mode, allowing you to choose whichever stage you would like to race in, who you would like to use and who you would like to race against, though you also can attempt to achieve a few goals with this such as getting a certain number of Rings or hitting your Rival a certain amount of times. Adding to that, there is a Cup Circuit mode which is similar but you're going for the best two out of three.
You also can collect cards, trade them, or wager them in the multiplayer races. 150 cards to collect in all. Generally easy to get the cards; just beat a goal in challenge mode or go to story mode and beat a Rival there.
Adding to that, this game also sees the return of a familiar face (one in which many Sonic fans will be pleased to see - he's an unlockable character) and it is very pleasing to know that he is in another Sonic game. That's one upside.
Either way, Rivals was a lot closer to being similar to the classic games than next-gen was, though probably not as much as Sonic Rush. Some Sonic fans might want to try this, as may some fans of racers. It's nothing special, but it's better than some other recent efforts.