Here are my top reasons:
New Zealand, land wise, is about the same size as the United Kingdom and Japan, but with a far smaller population. With only 4.5 million residents in comparison to the UK's 64 million and Japan's 126 million, New Zealand is truly a destination with plenty of elbow-room. Auckland is the typical big city, but once outside the city limits you'll find little to no traffic, easy driving and few crowds.
It's amazing how diverse New Zealand is, between the north and south islands as well as each island in of itself. On the North Island, you can explore for weeks the beautiful beaches, rolling farmland, volcanoes, geothermal hot spots, Lake Taupo (the size of Singapore), the wine regions,. The South too has its wine regions and its share of national parks, like Abel Tasman, plus the Southern Alps, glaciers that meet up with temperate rain forests, and not to forget the beautiful fjords. These are just the highlights - believe me there is oh so much more.
New Zealand has experiences for just about every type of vacation: Adventure, wildlife viewing, luxury lodges, relaxation and spas, culture and art, sports (rugby, sailing, fishing), sightseeing. From bungee jumping to fly-fishing to relaxing in a geothermal spring, New Zealand is perfect spot for multi-generation travel given the variety of activities for all types of interests.
Tramping? That's Kiwi for hiking! With 13 national parks and over 8700 miles of tracks, there are plenty of areas to take walks, ranging from a few hours to days. New Zealand rates its tracks by levels, with 1 being very easy (accessible with wheelchairs) to 6 for those seeking extreme adventure. And for people (like me) who prefer a bed, hot shower and great meal after a terrific day of hiking, many of the tracks have conveniently located lodges, from basic to luxury. The Milford Trek has been on my wish list for a long time, and knowing I can from hike hut to hut, not having to carry a tent, sleeping bag, etc, makes it even higher on my list of adventures.
Prefer to cycle? New Zealand has plenty of cycling tracks as well, some suitable for mountain biking.
Maori culture is a big part of Kiwi life and provides exceptional and unique experiences for visitors. Museums, performances, art, war dances, hangi feasts cooked in earth ovens or steamed in geothermal water - all authentic indigenous experiences not to be missed.
New Zealand 's cuisine is driven largely by local ingredients and has taken on a unique Pacific Rim flair. Plenty of seafood (greenlipped mussels, lobster, Bluff oysters, fish) local cheeses and not to forget (my personal favorite) famous lamb.
Visiting New Zealand's wine regions can take you from the tip of the North Island all the way down to the Waitaki Valley in North Otago near Queenstown. Check out Waiheke Island, a short ferry ride from Auckland, with its 40+ boutique wineries, Hawke's Bay, New Zealand's oldest and second largest region that dates back to 1851 or maybe the Marlborough area, New Zealand's flagship wine region known for sauvignon blanc.
Wine is undoubtedly a big part of New Zealand's culinary experience, but it isn't the only part. Kiwi's are also beer drinkers, and craft beers have been growing in popularity. There are over 150 craft breweries, with Wellington taking the lead as the Craft Beer Capital of New Zealand.
Thousands (millions?) of years ago, the New Zealand land mass broke away from Antarctica and Australia. This isolation has resulted in the area having unique plant, bird and wildlife only found in New Zealand. The most well known of course is the endangered kiwi, a nocturnal, flightless bird. But New Zealand has a large number of unique species, including the tuatara, a reptile with a third eye, the yellow-eyed penguin found in the south and the endangered Hector dolphin.
While not a unique species, the Otago Peninsula near Dunedin has the world's only mainland breeding colony of the albatross, and is home to both penguin and fur seal colonies. Whale and dolphin watching is popular in Kaikorra (just north of Christchurch).