As someone who owns a SNES and a TG-16, I think I disagree. The TG-16 graphics really pop compared to the SNES.

The SNES can only render 256 simultaneous colours. The TG-16 could do twice that at 512. Its video processor was also full 16-bit.

I’m not sure where you’re getting that the video was the weakness of the TG-16. At the time, that was the Turbografx’s whole claim to fame in that it was superior graphically to the SNES.

Source: Old enough to remember the commercials and bought both consoles to compare like nerds did back then

The PC Engine could theoretically do more colours on screen (though things like colour math and mid-screen palette changes do complicate that a bit...), but only had 9-bit wide palette entries compared to the SFC's 15-bit colour depth, which allowed for a lot more subtlety and richness.