I-70 from Denver to Grand Junction. Curves, hills, straightaways, tunnels, views of 14ers, rivers, ski resorts. Absolutely the best.
Drove the Taconic Parkway once in the fall, what a great beautiful twisty road with no trucks allowed. The leaves were kicking up, it was surreal.
I-17 from Phoenix to Flagstaff. You start with desert and end in the forest at 7000 feet. All kinds of topography. For added fun, cut through Sedona for some nice scenic twisties.