Adobe (1982), Intuit (1983), Electronic Arts (1982), Activision (1979), Symantec (1982), McAfee (1987)
Nintendo should probably be on that list with EA & Activision as well. The only reason they still exist is due to their consumer software business. They've shipped an enormous amount of consumer software.
Microsoft hasn't been a pure-play software company in a very long time. So I would also include Apple and IBM on that list, as both have shipped huge volumes of consumer software at various points (Apple is both still alive and still ships consumer software; IBM still exists, but no longer ships consumer software).
Just down the road from me is Frontier, which was founded by David Braben. He was working on the original Elite back in the early 80s, and although Frontier didn't come along until a decade or so later and doesn't strictly meet your condition, I'd argue that it's a good example of a successful consumer software business and has got there by producing a sustained track record of successful products. A few years ago it was listed on the stock market, but by then it had already managed almost two decades as an independent and grown to hundreds of people.
Others have, but Microsoft always been primarily B2B/Enterprise, not primarily consumer.
For that kind of company from the 1980s or earlier, MicroFocus.
> In contrast, I can easily name dozens of companies in other fields that have been around for 50 years or more
In any one field, though? And one as young as software?
Lugaru Software [1] (Epsilon Editor) has been around since 1984
There are more but...
In contrast, I can easily name dozens of companies in other fields that have been around for 50 years or more, including some small ones that have stayed small yet successful.