In 4-quart saucepan, evenly sprinkle unflavored gelatin over 2 cups water; let stand 1 minute to soften gelatin slightly. Cook over medium heat, stirring frequently, until gelatin completely dissolves. Remove saucepan from heat; stir in cherry and lemon/lime flavor gelatin until they completely dissolve. Stir in 3 cups cold water. Refrigerate until mixture mounds slightly when dropped from a spoon, about 1 hour.
Meanwhile, coarsely chop cranberries and mince celery; place in medium-sized bowl. Add drained pineapple and sugar, stirring until sugar completely dissolves.
Fold fruit mixture into thickened gelatin. Pour into 10" Bundt pan or 12-cup mold. Cover and refrigerate until set, at least 3 hours.
To serve, carefully unmold gelatin onto chilled platter.