There are three areas that are the best of New Zealand - to me anyway:
Queenstown. There are tons of things to do: Wineries, art galleries, hiking around Lake Wakatipu, tennis, jet skiing, bungy jumping, and white-water rafting.
Want real peace & quiet? Rotorua - Lake Tarawera (Central North Island - about a half hour from Auckland). Check it out, if you like to get away but still want to do things like water skiing, mountain biking, kayaking, and touring by floatplane.
Back to civilization: Christchurch. This is South Island (Canterbury). If you want art galleries, balloon rides, museums, the botanic garden, golf, and the best part of the Southern Alps.