I'ld agree that they all have their simularities, but they still all manage to have a different feel. 1 really does bring up the memories of childhood and has some very fun music (like the Pizza Planet.)
2 has Woody's Roundup, and Jessie's song of course.

The music is certainly more dramatic and powerful. And 3 is the accumilation of both the previous films, taking all the greatest themes, and adding some real suspense-building scores to it aswell.
For me, it's Toy Story 2, since I just love the Woody's Roundup music, and When Somebody Loved Me
