1. Heat oven to 350° F. In medium bowl, combine butter and crushed gingersnaps. Press mixture into 9-inch springform pan, working crumbs over bottom and up sides. Bake for 20 minutes.
2. In small bowl, toss pears and ginger. Line cooled crust with pears, overlapping slices slightly. In large bowl, with electric mixer on medium, beat cream cheese for 2 minutes. Add 1 cup of sugar and beat for 2 minutes. Add eggs, 1 at a time, and mix until combined. Stir in 2 tsp vanilla. Pour mixture over pears. Bake until top is barely set but still slightly wobbly, about 50 minutes. Transfer pan to wire rack, leave oven on.
3. In small bowl, combine sour cream and remaining sugar and vanilla. Pour over cheesecake and bake for 8 minutes. Transfer to wire rack and cool to room temperature. Cover and refrigerate for at least 4 hours before serving.