I dare say NEW 28 gauges outsell 16s, and there are certainly more being made. The 16 lovers are always trying to rally new members to the cause, but ever since the advent of the 3" 20, and the fact that the 16 was left out of all gauge skeet competitions, the 16 has been languishing. Unless you pay the money, most 16s, especially repeaters, for a long time have been built on a 12 gauge sized receiver, and that negates many of a 16's attributes. The 28 has suffered some of the same issues relative to gun size, but is still currently available from a number of manufacturers, and of course it is still used in all gauge skeet. Just go to GunBroker and look up 28 gauge semi autos. The Franchi 28 semi is probably the absolute lightest good game gun you can buy.
When you get into the really good double guns, with receivers scaled to the gauge and well balanced, the fact is every gauge gun feels great, not just 16s or 28s. The 28 is a grand bird gun, and let's face it some people get a sense of one upmanship versus the guys with 20s, the same way the 20 guys felt about 16s and 12s. And the 28 performs quite well with the right loads for the game - usually better than many would expect.
I love the 28, but never had much use for the 16. I am sure there are lot's of 16 lovers who feel the same about the 28; it's all a matter of personal preference.