Columbus and Denver are about 1,164 miles apart by road. Split the difference and you arrive near Kansas City, the city closest to the halfway point between them. That puts roughly 12 hr 59 min of driving on the Columbus side and 11 hr 41 min on the Denver side — the fairest single meeting point among the cities near the middle.
Over this distance most people will fly rather than drive the whole way. Kansas City still makes a fair, central place for Columbus and Denver to converge, splitting the travel instead of asking one side to cross the country.
If Kansas City doesn't have what you're after, Omaha and Minneapolis are also close to the midpoint and worth a look — each keeps the drive reasonably balanced between Columbus and Denver.
City descriptions adapted from Wikipedia (CC BY-SA); photos via Wikimedia Commons, credited above.