After riding it, though it's not terribly long, I'd nominate US-6/191 between Price and I-70/US-50 and I-70/US-6/US-50 from there east through Utah.
Considering the scenery through Spotted Wolf Canyon (on I-70/US-50 west of there) and the Moab area to the south of Crescent Jct., the contrast between colorful red rocks and the bland grays and yellows is pretty jarring.
While I haven't driven it yet, I'd also nominate I-80 across the Bonneville Salt Flats. You'd appreciate its stark beauty for the first time, but having to cross the Salt Flats on a regular basis would likely get old. For that matter, regularly driving on any road in Utah's west desert would soon become boring. At least there's a lot of sagebrush there and in Nevada, which you can't say for 6/191 or 70/6/50/191.