The SG-1000 was basically a crummy ColecoVision clone; same video chip, Z80 CPU, and all the limitations that came with it. It was hotrodded into the more capable Mark III / Master System, but even that wasn’t exactly cutting edge compared to what Nintendo managed with the Famicom.
Meanwhile, despite a smaller palette, the Famicom/NES’s custom Ricoh PPU was incredibly advanced for its time. Devs squeezed amazing results from it thanks to clever hardware mappers, scanline interrupts, and tight hardware integration, features that weren’t really viable or widely used on Sega's 8-bit consoles.