The Mazda 5 which is based on the Mazda 3 is a Mini Minivan that is poorly advertised and not many people know the car exists which is sad because its a solid vehicle if a bit underpowered. Its a great all around value for the money.
Another car is the Ford Fusion which is underappreciated and it's not as popular as the Honda Accord and Toyota Camry for example. Some people like it, some don't. It has an excellent reliability record and is a fun factor vehicle to drive and experience.
My third choice is the VW Tiguan SUV which is a great vehicle offered by VW but not many are sold due to VW's reputation of electrical issues and questionable reliability. Another negative for the Tiguan is its fuel economy which isn't impressive. The Tiguan in my opinion is better looking than its big brother Touareg. If VW ever considers putting the VW Jetta's TDI Diesel engine on the Tiguan they will have a hit possibly taking sales away from the other Small Utes like the Toyota Rav4 or the Honda CR-V.
My second to last car is the BMW 1 Series Coupe. While it is a great car offered from BMW it is still too expensive to consider buying. The car has style, a better looking interior than the current BMW 3 Series. Bottom line if BMW wants to sell more 1 Series Coupes they need to find a way by lowering the price by offering less powerful engines and make more equipment standard because for a few thousand dollars more you can get the more useful 3 Series Sedan with 4 doors.
My last car that I believe is underappreciated is the Subaru Forester. Its an all around great small SUV but it still has some negatives that can be easily fixed. One is the current 4 speed automatic transmission. Subaru needs to put a 5 speed auto in it to make it more fuel efficient. The second thing they need to do is make the interior look like it has less plastic. Use some higher grade plastics and make it more inviting to the driver to feel like he has a well put together car and less rattles.
It's too bad that some cars receive lackluster marketing and the public doesn't know more about these vehicles. Automakers in my opinion need to slim down the amount of models they make so the underappreciated models get some spotlight and consumers will get interested in them and consider buying one.