I'm sad as well, I first flew on an NZ 747 in 1997 on NZ2, and have lost count of the times I flew on NZ2/NZ1, NZ6/NZ5, NZ7/NZ8 and for the period it operated NZ38/NZ39 on the big birds.
From the Pacific Wave business class on the upper deck and downstairs (NZ's 767 business class is what remains of that), the 34" economy class downstairs (without personal video IFE of course) and about half a dozen times in First Class in the nose (the last time with actual first class service being an op-up on a full NZ1 from LAX when the 2nd LOTR movie was having its premier in Wellington, with the First Class cabin otherwise full of celebrities like Liv Tyler and Dominic Monaghan).
Those were the days when NZ1/2 operated from T3 at LHR using the United lounges that are now BA lounges, and the LAX NZ lounge was half its current size. However, they were also the days when the Business Class catering involved trolleys with grand plates of a wide selection of fruits, cheeses and desserts, where you could point out what you wanted and it got plated for you. The flipside is the 10 channel rolling selection of films and TV shows on the tiny IFE screen that flipped up, and reclining to an angle of 40 degrees or so (and first only going fully flat when a row was removed around 1999).
After the end of First Class there was the delight of always getting the nose when booking Business (or being upgraded with Gold/Gold Elite upgrade vouchers or airpoints upgrades) whilst being a Gold Elite, so having first class seats with Business Premier service. The last refurbishment was a distinct improvement and brought us premium economy, promptly expanded downstairs with a mini cabin that was quite pleasant. I never flew NZ in economy with the most recent configuration on the 744s, but there was always something special about flying in the nose in BP. It was also a time when you could sometimes find yourself with a celebrity discreetly flying NZ1/2 between LAX and LHR, enjoying this quiet low density cabin.
No 777 comes close... not as private, not as fast, not as impressive to watch, and certainly in Y - not as comfortable.
The end of an era, and almost the end of an era for New Zealand with 747s as passenger aircraft.
I doubt the passing of the 767s or 737s will be quite so missed, although the latter including their two previous generations, were transformative for NZ, ultimately being the death knell for railways as a key form of business travel, but that's another story.