Same thing I'd want to be "interesting" about any emulator. Focusing on just graphics for a moment (but there are equivalent examples in other domains):

1. Running games that only ran at 10FPS on original hardware at a smooth 60+FPS, by calling the game's own rendering logic more frequently than the original hardware could "afford" to, but without breaking game logic (i.e. by forcibly decoupling the game's physics ticks from its presentation ticks);

2. Using out-of-viewport but in-{tile/frame}buffer data to expand the viewport to fill my screen (which can be very janky under some rendering paradigms, due to offscreen parts of tile/frame buffers being dynamically partial-updated with a loading seam; but which can work very well under other rendering paradigms, like the SNES's mode 7 where the tilemap was usually just fully populated once at mode-switch time);

3. Making games that used vector-graphics for at least part of their display, and soft- or hard-rasterized those vector graphics into the native low-resolution framebuffer, instead rasterize those graphics at my display's native resolution;

4. having the emulator recognize particular bitmap assets (tiles, sprites, 3D meshes/textures) the game is telling it to render, and swap these out for hand-crafted HiDPI / high-poly versions of those assets from an asset-pack file (as opposed to relying on the caprices of a DLSS-like upscaling model.)

Mind you, to have features like this work well, they often leave the realm of "interpreting the control-register pokes from the game differently", and enter the realm of "the game being patched to take advantage of the capabilities of the emulator." Then, as with these GOG games, you're no longer just shipping a ROM "and an emulator configured to run it well"; rather, you're shipping a co-designed product: a specific emulator, and a ROM that's been tuned for that specific emulator.

Which means that you technically leave the realm that MAME-like "archival preservation" emulation usually aims for, of "faithful emulation" of both a game's logic and its presentation.

But, unlike with an actual "HD remaster" of a game, with this "enhanced emulation" approach, you can keep "faithful emulation of game logic" while only discarding "faithful emulation of presentation logic" (in favor of "more pleasing / legible / ergonomic presentation of game logic.") Which is, IMHO, a very nice point in the configuration-space of how these old games can be played, that a decent chunk of people prefer over either of the other two points.

Windows GOG DOS Games on M-Series Macs