H Peterzier -
<<"Lake Neauchatel, Glacier Ex., St. Moritz, Innsbruck, Salzburg& Garmish Bavaria, Zugspeitz. Didn't go to Interlaken to view that part of the Alps. But they say the Matterhorn is the most viewed mountain in the Alps.">>
Quite a trip. I've not see the Zugspitz nor been to Garmisch, so I can't judge those. Certainly, the Matterhorn and Zermatt would be the most impressive of that list within Switzerland, for me as well.
However, in my opinion, the Jungfrau region (not Interlaken) offers a comparable experience, over a much larger area, with more opportunities for varied viewpoints and hikes. So, you might consider a look on your next trip, and see what you think.
As for most viewed, I offer another thought.
The Matterhorn can be seen from many directions, and many angles. Mostly from the less populated regions of Switzerland, Italy and France. However, the Jungfrau massif can be seen from Bern, the Lake Neuchatel region, Stanserhorn, the Emmental..... That means a lot of people get to look at the Eiger, the Mönch, and the Jungfrau ( and more) every clear day from all over Switzerland.
Of course, it is not "up close", but to be precise - the millions of people within those regions outnumber those who get to see the Matterhorn from Zermatt, or Fiesch, or the Gemmi Pass or other high viewpoints.
To illustrate my point, I've attached views of the Alps from the Dreiseenland ( Three Lakes Region), and the Emmental.
Just kidding about the number of viewers, but when you return to Switzerland, you'll have a lot more ways besides Zermatt to see more beautiful mountains. ;-)