Interviewers often ask questions like this for a couple of reasons. Chances are, whatever characteristics you would consider valuable in another person are characteristics that you possess. Your answer will give the interviewer an idea of what to expect from you.
"I believe a nursing aide should be outgoing and love people. This is a great job, but it requires a lot of hands-on activity with patients. Being comfortable getting to know people is essential for this job."
"A nursing aide should definitely be flexible and easy to get along with. Working with people and coordinating daily care requires attention to detail and flexibility."
"I feel that a nurses aide should be focus driven, but also flexible. He/she should also be a great communicator, as we provide care and assist with activities of daily living for those who can't always do for themselves. A genuine love for people and a giving spirit are important."