I'm a big fan of isometric view RPGs (you know the ones...). I was looking through the RPG month sales and realized that it would make my life so much easier to be able to filter for only isometric games - or, at least, "overhead" games. I imagine some people feel the same about third person ("over the shoulder") or first person games.

That would be a nice thing, but that'd require GOG to pay attention. And curate.

You'd be better off using the Mobysearch or GOGDB to curate your desires.

This would certainly help.

The third-party site GG.deals has a powerful advanced search that can accomplish this and more:
All isometric games on GOG

As with any question about “categorising” things, where does it end? Is a movable camera still isometric? What about a camera you can zoom in from isometric to first person? Categories really only give the simplest of overview of a game at the best of times, you could have a real time strategy and RPG as isometric (and in fact most other games), so how is camera filter going to help? Is Skyrim or oblivion a bad game because they don’t have isometric point of view (mentioned as you are obviously talking about the infinity engine games)? Going down this route every game would end up with thousands of different tags for different people, and then we would need a new tag system to find things in the tag system!

There's no need to take this to absurdity. A simple categorization of "side-scroller", "overhead", "first person", or "third person" will include the vast majority of games. Games permitting multiple viewpoints could be listed under multiple tags.

So if there's any difficulty in implementing a feature, you just don't do it? Do you work at GOG?

Yes, but you see that’s just some tags you want. These threads pop up all the time, with other necessary tags. People argue on the tags which are already available as to their definition. As I mention before what about games which allow you to change the camera? Then you have various tags for that, as well as various tags for game type, multiplayer type etc. It’s easy to say it’s just a simple categorisation for one person, but when there are hundreds of requests for different tags….
It’s a JWSaRPG side scrolling third person overhead strategy fantasy adventure hack and slash …
Far better to simply read some reviews, watch some game footage and see if it is a game which would interest you rather than trying to find specific classifications (which really don’t say anything about the game).