I believe a key part of the issue is directionality. If you decide you love games so much that you want to open a game store, you're going to do poorly. If you have the desire and skills to go into business for yourself and want to work locally in a retail setting, and you decide to put your hobby to work and use it to help you, you have a good chance.
The closest analogy I can think of is dog lovers and veterinarians. Some kids really love dogs. So much so that when you ask them "what do you want to be when you grow up" they say "I want to be a vet so I can help dogs". But once you go to vet school and/or intern with a real vet, you're going to be faced with some uncomfortable truths.
First, you don't get to just be a dog veterinarian. You get to be a vet for whatever animals you can get business treating. It doesn't matter how much you hate cats, if you're a vet you'll eventually have to treat one. Second, being a vet doesn't always mean making dogs healthy; sometimes it means putting them down. If you love dogs so much that you can't kill one, you simply cannot be a good vet. This will become ever more of a problem on the day when you have to make a cat you hate healthy and kill a dog that you love. Third, you'll be forced to deal with the people you hate most: people with dogs who abuse them, or people who ask you to perform unnecessary procedures that you feel are unethical. You will deal with these people on a daily basis. And finally, no matter what job you take, there's going to be monotony. At some point in your career, your love of dogs will lead you to an entire day (maybe a week, maybe more) of doing nothing but removing dog testicles and uteri. And that will not be a fun day.
Gaming stores are exactly the same. If you love gaming so much that you want to start a store, that's great. But that game store is going to attract Twilight nerds. And you're going to have to lower stock on your favorite game books if it doesn't sell, and increase stock in Twilight books if that's what sells. And you're going to interact with edition-warmongers and closed-minded parents. And at some point you're going to spend an entire day behind a register.
Liking what you do is critical to enjoying life, and hobby stores absolutely require a certain about of emotional investment. But they also require at least some degree of emotional detachment. You have to make the hard calls. You have to deal with the BS without allowing it to taint the thing you enjoy.
Hobbies like gaming (or animals, or
bendy straws, whatever) can be a good compass. They can point you in a general direction, and can be a good reference to remind yourself where you're heading and why. But they're not a roadmap for life. Try to follow one too closely, and you'll end up more lost than you started.