Accessory Apt or NICE Movie Theater Rm? What Adds More Value?

[Chris Watkins]

I just closed on a new primary residence for me and my family here in Utah. The intent was to buy a home with awesome potential that we could work on for the next 3-5 years (build sweat equity) then sell for a nice profit. The basement is unfinished and I want to know what will bring more value to the home - adding a legal accessory apartment or a nice movie theater room in the basement?

More about the home, neighborhood, and long term plan:

Maybe a little more about the home will help shed light on the decision. This home is really custom with high end unique features like incredible 40 ft vaulted ceilings, sky light windows, custom mosaic travertine floors, archways, radiant heat in the floors, lots of land right against the mountain with incredible views, orchard, and over 3000 sq ft in main and 2nd floor living (not including basement sq ft). Basically, the home has high end potential but the previous owners sort of let the home and yard go - so we got an incredible deal on it. 

The neighborhood is nice (all homes built after 2000) but not all custom like this home. 

Long term plan for this home is to live in it for the next 5 or so years while putting sweat equity into it - making it feel more "high end". However, I do realize that there is a chance that we will not want to leave...

Which Should I Do? Accessory Apt or Movie Room/Man Cave?

In the end, I want to know whether I should work to get a legal accessory apartment permit for the basement and finish it as a rental income source to offset the mortgage, or whether I should go all out and add a nice movie theater room / man cave. 

What do you think will add more value? I think they may end up costing the same amount to finish due to the fact that I would have to knock out a wall to add a separate outside entrance and a few other things for the apartment.