There are many different types of radio contorled cars. These range from toy grade(radioshack, toysrus, ect.) to hobby grade cars. Hobby grade cars offer much more tunablility, durability, and most importantly performance. Hobby grade cars can be modified and upgraded, while toy grade cars can't. Hobby grade cars are also made of more exotic materials, such as carbon fiber, and in some cases Titanium.
Toy grade radio controled cars can be great for little kids, but adults will easily get bored with these. They are great for beginners, and come in many different styles.
Hobby grade cars, on the other hand, require mechanical skills to build, use, and fix. This presents a much greater challenge. These cars can also cost much more than toys. There are many organized races for different types of cars throughout the world.