@lfa The Amiga could be regarded as 32-bit: its CPU has a 32-bit instruction set. Also, all released MSX2+ computers had just 64KiB RAM. (Expandable, as per standard, but still..) It all was kind of fluid back then :)
Graphically, I guess VRAM, width of datapath and hardware acceleration, blitter and tricks were what was most visible. Amiga had tons of those. MSX2's VDP was just 8-bit, albeit with some hardware acceleration.