I'm on the wrong part of the bell curve as a collector, a rider, and a photographer compared to most folks in the C&V forum. I'm probably on the right part of the bell curve as to age in this forum, but only by a couple of years.
I have a deep philosophical hatred for the concept of favorites - it's a question you ask a four-year old because you can't have an adult conversation. But I finally clicked on this thread and saw that Adventure Man brought the discussion into the adult realm by framing it in terms of thinning the herd as we all get older, so here I go.
Most comfortable is probably a 1979 Trek 710 that I got from the co-op. It has a lot of patina but I love that metallic dark blue so I stripped it, scrubbed off the rust, and clear coated it, then mostly put the parts back on it that the original owner had donated it with. I think I reduced the chain ring size a little because I'm a wimp. I also have a 1982 710 in better shape. It's nice but not quite the same as the older one.
The one I get the most compliments on is kind of a joke build of an awesome late 1980s Montagner racing bike frame. I'm not a racer so I built it with stem shifters and turkey levers for city riding. Bike people and non-bike people alike say "nice bike" when I ride this. Well, OK, bike people say "nice frame."
Last one to get sold, even though I don't ride it as much as some others, is probably the 1983 Paramount Elite. This is the only one that I would consider putting in a show for collectors to look at.
I just did a 650b conversion on my 1982 Claud Butler Dalesman, but I don't have a picture of the build yet. I have several older bikes but they're not high end and probably do not make it into the low single digit number of bikes I would keep if I had to move into a senior apartment.