Classic SSAO is very similar to performing an "unsharp mask" based on the depth buffer. This has been proposed "a simple and efficient method to enhance the perceptual quality of images that contain depth information" in the paper "Image Enhancement by Unsharp Masking the Depth Buffer" which came out a year after SSAO was published by Crytek.

https://www.uni-konstanz.de/mmsp/pubsys/publishedFiles/LuCoD...

Nowadays it’s common for SSAO to actually do local radiosity approximation via ray marching. But back in the day when this article was written, that was too expensive so you approximated it by detecting sharp transitions in the depth buffer.

For a benchmark you can just use a "vfx/cinema grade" path-tracing renderer of the same game scene?