Hello and welcome to RTA !

A common theme you will notice on the forums is that there is no one 'best' route or attraction as each person and their trip is unique, but for scenic beauty I would look at I70, possibly cutting down to I40 via US191/163/160/89, which takes you close to Arches and Canyonlands NP's, Monument Valley and the Grand canyon south rim. Before this you could detour to Rocky mountain NP, drive over Loveland Pass and along the rim of the Colorado National Monument. After GC you could visit Vegas, drive through Death valley and into Yosemite NP via Tioga Pass [CA120]

The point being is that this just one route option naming just a few of the possibilities along it and there are hundreds of possible options. What you need to do is a little research and take a look at good maps and see what appeals to you. Once you have a few of your own ideas we can help piece them together and make suggestions. The longer you have the more you can see and the difference between 1 week and 2 weeks is quite a big deal.