A great improvement over it's predecessor in almost every way...
The game consists of 8 playable characters total which includes Sonic, Shadow, Knuckles, Silver, Metal Sonic, Tails, Espio, and Rouge. All of them play the same but with different specials such as Sonic's speed boost or Shadow's chaos control. Like the original, the main gameplay is 6 well-designed levels where you and a "rival" have to race. Every stage has 4 acts. Act 1 is a race, act 2 is a battle, act 3 is another race, and act 4 is a boss battle. However, unlike the original, there is now a "battle mode" thrown in with six game types such as knock out, tag, capture the chao, king of the hill, laps race, and ring battle. All of them are pretty fun and great additions to the game (except maybe laps race, all you do is race through only part of a racing stage over and over which isn't as fun). Instead of doing challenges in each stage to unlock a card, you have to complete a certain "achievement" to unlock certain content which is mostly outfits for your character to wear. I just wish there were more than 6 stages.
In story mode, all 8 characters are split up into four teams (Sonic & Tails, Shadow & Metal Sonic, Knuckles & Rouge, Silver & Espio). When you choose a team, you then choose one of the characters and play through the stages. The story is that the chao have been mysteriously disappearing and it is up to Sonic and his rivals/friends to get to the bottom of this. The story mode has the letter boxes like the original but it also has full voice overs instead of a bunch of "heys" and "whats". The voices sound about the same as always.
The music is still about average except the main theme "I Always Race to Win" and Blue Coast's act 3 music.
There is more value in this version than the first with more stories to play through, more outfits to unlock, and more cards to collect.
As for multiplayer, I don't know anyone else who has this game but I do know that there is gamesharing this time in which you can play each other with one copy of the game. The only problem with multi is there is no online, something they should have put in.
In conclusion, Backbone has made another great Sonic game for the PSP and I recommend anyone to try it out. The levels are as well designed as the first if not, better, and practically everything is improved. Don't listen to the critics, Sonic Rivals 2 is very fun and very underrated.