Hello, Jack! The correct phrase is "the best place in the world." You use this when referring to a particular (only one) place that you consider the best among the rest. Also, there should be "the" when using the superlative form of an adjective. For example, "The most important person in my life is my mother." Similarly, you can say these patterns: (1) The best place in the world is (name of the place).; (2) (Name of the place) is the best place in the world.
Regarding the second part, the proper way to say it is "I've got a question for you." You shouldn't use "to" in this structure. Remember that you've got something, like a gift or a question for that matter, for someone. :)