Dissolve gelatin in 1 1/2 cups boiling water.
Add 1 1/2 cups cold water. Mix liquids from fruit and measure 2/3 cup; pour into the gelatin mixture. Stir and chill until slightly thickened, or a thick, syrup-like consistency.
Dice pears and add to the gelatin mixture along with the crushed pineapple and sour cream. Mix thoroughly. Pour into a 6-cup mold or use two 3-cup molds. Chill until firm. Unmold onto salad greens and garnish with grapes or other fruits.