FM radio sensitivity is measured in dBf. The lower number the better. Some poor quality stereos have number around 12 or higher. Most good quality automotive radios have a sensitivity spec down around 8 or 9.
An online retailer like Crutchfield will give you this spec. and many others about each stereo. You can compare and find one with the best sensitivity. There is a huge difference between a factory stereo and a good quality aftermarket one.
I will also agree that satellite radio is an excellent alternative. They have something for everyone. I can't imagine how someone couldn't find something enjoyable to listen too. I have a subscription where I pick out 50 channels. It costs less than $10 per month.