The answer depends on your neighborhood. If you live in a three bedroom, 2 bath, 2 car garage area, then you will probably not see you house value go up much. But if your new 2 car garage only cost $10,000, then that is the most you can loose. I used to live in a starter house neighborhood, and I will say I would easily pay 5k to 8k more for house with a 20x20 shop in the back yard.
At some point you are throwing money away and need to consider moving to a more expensive area, and buy a cheaper house relative to everything else on the street. Then, when you spend 10k to 20k on a garage, your sale price maybe the same as the other house on the street. You never want to own the most expensive house in the area, you can never get you money out of the house, due to all the buyer comparing your house to comps on the street.
Now my current house is a 4 bedroom 2.5 bathroom neighborhood, 2,600 sq ft minmum. My house does not have a basement, and cost less than the ones that do. I am building a 26x44 two story garage that will have 2,100 sq ft floor space and a 300 sq ft attic storage area. Will I see my house value increase at sale time? Yes, but probably not as much as I would like. My wife and I are building the garage, so I am only paying for the material, plus one long year of working all the time on the building.
I have a friend that bought a house last year, they looked all over my area for a three car garage. Never found one in a "normal house". You have to buy an "estate house" to get a three car garage. So when I goto sell my house (not for a long time...) I may have to wait a while for the right buyer, but they are there and will pay extra for a house that you can park 6 cars in. My ceiling is 12.5 ft tall, so I could but four storage lifts in my new garage and store a total of 10 cars. Currently I have my RV inside the garage, so an RV owner would love my garage's 11 foot tall door and 44 foot long inside.