There are quite a few brands that are much better than people think, at least right now. I'll name the top 10:
1. Hyundai
2. Saab
3. Infiniti
4. Subaru
5. Acura
6. Select Dodge models*
7. Saturn
8. Volkswagen
9. Lexus†
10. Audi
This list goes from most underrated, #1, to least-underrated (or most well thought of), #10. For example, people who generally aren't interested in cars think Hyundai makes low-quality, inferior products. They usually know that Audi is a luxury brand, but don't think it's as nice as BMW or Mercedes-Benz.
*Caliber, Nitro, Charger, Magnum.
†As a twist, most people who generally don't read about cars think Lexus is a high-profile brand, while auto enthusiasts believe Lexus is a blatant Japanese ripoff of Mercedes-Benz, a.k.a "rebadged Toyotas".