I'd like to put my 2 cents in, if anyone wouldn't mind:
NiGHTS: Journey of Dreams, gets a 7.5/10 from me.
The graphics were sub-par, they could have been better. The movie-cutscenes were outstanding, but gameplay/normal cutscenes could have been very much improved. The main thing that saved the game for me was gameplay (the part that matters), the music, and the fact that I think this game can go competitive. People say that one can go infinite score. I've tried this, and the timer counts more towards your score than going through rings does. Also, it's very difficult to not beat the level and keep your score chain going.
I love this game, it will keep me occupied until the release of Brawl and probably even more afterwards. The bosses were annoying (some of them, others were mad fun) and the game overall is a very very fun game to play.
I feel, though, that Sonic Team could have easily made this a far better game. I could have waited until next year without any complaints, because it could have used some serious work. Without the help of Yuji Naka, however, I feel that the creators of the game did very well in making the gameplay what it was supposed to be.
Like I said, gameplay is awesome. If you care more about the story/graphics, it sucks. Otherwise, most other aspects were very very good.