I enjoy the drive down River Road up in the Oscoda/Tawas area. We are usually up there twice a year for autox's at Wurthsmith AFB and stay at a buddy's cabin about 30 mins away. Unfortunately, we are usually driving a tow vehicle when we head back, so it's not quite as enjoyable.
M-23 / North Huron Rd up the coast from Standish to Oscoda is a really enjoyable drive as well.
South East MI is pretty lame
most enjoyable twisty roads are dirt, and hardly ever in good shape.