For 2 weeks, I would recommend seeing the national parks in the 'mountain west'. Each of these could be a 2 week trip. I have taken each of these road trips and had an awesome time!
1. Fly into Salt Lake City. Drive south through Utah and stop at Zion National Park, Bryce Canyon National Park, Capitol Reef National Park, Lake Powell, Canyonlands National Park, Arches National Park, then head back to Salt Lake City.
2. Fly into Salt Lake City and head north to Jackson Hole, WY. From here, you can head up to the Grand Teton National Park, and Yellowstone National Park. Then head back.
3. Fly into Denver, CO. Stop at Estes Park National Park. Head south to the Great Sand Dunes National Monument, and then west to the Durange area to Mesa Verde National Park and the 4 corners region and Monument Valley. There is spectacular scenery there. You can make a loop then by driving north through Grand Junction, CO then back to Denver. The mountain scenery is amazing in northern Colorado.
4. Fly into San Francisco, CA. The San Francisco area is great to see, it's a fun town, maybe not so much to drive an RV around though. Head north over the Golden Gate Bridge, and you can then make a loop by heading north up the coast, then east into the Napa Valley area for some great wine tasting, then head over to Yosemite National Park and Sequoia National Park, and back to San Francisco.
Any one of these trips will be awesome, I promise!
You can get more info and pictures of some of the parks at the website below.
Have fun :-)