Why not 386? (This question came on reddit)
The problem is that all 386 systems use ISA graphics cards. ISA is slow, it supports max. 16-bit data transfer width at 8 MHz, some ISA graphics cards achieve transfer speed only 1–2 MB/s.
A 320×200x8 screen contains 62.5 KB of data per frame. At 30 FPS, approximately 1.83 MB of data must be transferred every second. At 386 there is a very little time left for per-frame calculations. This is why 32-bit DOS/4GW games cannot run at full screen with an acceptable frame rate on a 386.
By comparison, VLB and PCI graphics cards can be 10–20 times faster at data transfers.