actually they are quite intelligent, and many people with the ability to keep them find them very appealing. they can be hand fed, eat from your fingertips, come to the top of the tank for a petting, and can develop some really amazing coloration.
"common" is just what most people call them because they are the most often seen, almost everywhere. other people with more background call them by the scientific names, which are more appropriate. Commons only reach 20-24", and will be fine in a tank 2-3ft. wide with at least 150g's. Saying they need a pond is a bit of overkill.