PlayStation outputs in both 240 and 480 lines. 480 lines don't look nice with filters unless you use a resolution that is a multiple of 240 (but not 720p because it's too low and will again be upscaled to 1080p by your monitor/TV).
You'll need a minimum native resolution of 880 lines (non-existent). The closet native resolution to a multiple of 240 on a commercial device is 4k (aka 2160p). This is impossible for gaming on a Pi.
I would recommend playing around with different shaders because I remember that some use tricks that simulate interlaced picture on 480 rendered lines, resulting in a shaky but more pleasing effect.