While I'm glad GOG's got such a large catalogue these days, is there a way to list only DOSBox/emulated/classic/old games?

Not really.
The store allows you to filter by "Classic", "Only on GOG" and/or "Good Old Game".
Maybe that narrows it down a bit?

Edit: forgot about the "Good Old Game" tag.

Edit 2: I'm sure you know that, but just to make sure: the more filters you set - the less games you'll be shown, so...try each tag for itself, before you try two or more.

There is no reliable way to do that. You can try tags like BreOl72 suggested, you can try to narrow release date to year 2000 or even earlier.

You can filter by release year, for instance:
https://www.gog.com/en/games?releaseDateRange=1980,1995

Some older games might not have the right release date in the catalog, but that will at least exclude newer games.

Thanks all - looks like my edit didn't go through - the release date range worked for me.

Beware that some games have a release date on GOG, and not the original release date.

For example:

This is a 1995 game, but with a 2023 release date:
https://www.gog.com/en/game/renegade_the_battle_for_jacobs_star

Or this one from 2005, again with "released in 2023":
https://www.gog.com/en/game/boiling_point_road_to_hell

I suggest three ways to find old games:

Release Date
OR
Tags ("Classic", "Good Old Game" etc.)
OR
Check specific catalogs of publishers/devs specialized in old games (SNEG, Ziggurat, Atari, Nightdive, Digital Eclipse, Throwback, Piko etc.)

The best way is to use other sources to compile a list of games that you might be interested in, and then check if GOG has any of them in their catalogue.


Otherwise, in addition to what other have suggested, you might want to bookmark this URL that is often forgotten:

https://www.gog.com/en/good-old-games