This is a tough one to answer, as reliability depends on how you use your car. Cars are all different, and they are all unreliable in their own way.
If you never take your car anywhere but to the grocery store, then a small Toyota Corolla will be very reliable. On the other hand, if you put on a lot of miles on your car, it will require frequent maintenance and will be a lot less reliable. There are some car manufacturers that are better than others when it comes to reliability, but they too will vary by model.
Toyota and Honda tend to have very reliable cars, but don’t rule out American brands like Ford and Chevrolet. If you are looking for a new car, read reviews, talk to people and do your homework before deciding on one brand.