Halo 2 640x480 SSAAx16 perfect scaling to 8k (lossless upload)
This is intended to be watched at 4320p60 (8k). Not for the pixel count, but for the higher bit-rate and better video codec.
This may be the highest quality standard definition video on YouTube at the time. This is possible because it was intentionally forced into getting the same video codec settings and compression level as if it were an 8k video when it was re-encoded by YouTube.
Rendering Info
This was rendered at 5120x3840 (That's ~2.4x more than a native 4k resolution, nearly 8k but 4:3 aspect ratio) then downscaled to 640x480 and losslessly captured.
It was then losslessly upscaled and encoded through FFmpeg, with a nearest neighbor filter, to 5760x4320 to be YouTube friendly. (8k integer scaled, 230GB total file size)
Achieved with ValveSoftware's GameScope for Linux. Special thanks to @RuanEvangelista