I'm ready to be flamed for this, but considering I got it for $25, i'm really quite enjoying sonice unleashed, and I plan to get all the medals, time trials, etc.
That being said, while it's much more polished than the precious outing 06, the framerate issues still linger and playing as the wer-hog get's a tad tedious and tiring.
Some games that are worth finishing 100%?
I think MGS4 is quite an experience, trying not to kill anyone, or, be spotted once. LittleBIGPlanet is just a fun game, and if you are good enough, that's fairly easy to finish 100%, Soul Calibur IV (i liked it), Bioshock (both run throughs good and evil), Resistance 2, Valkyrie profile (getting the A ending, can be tough, but worth it), Gurumin (another really fun psp game), Shadow of Chernobyl (the good ending has the best plot). That's all I can think of off the top of my head. Despite what people say, steer clear of Oblivion.