I must agree both with rockersuke and skurk.
- Comparing MSX with Amiga is simple impossible. Amiga is so much powerfull that you can create very nice and addictive games using Game Creation Tools. Nevertheless, it's much more powerfull hardware would require much more human effort to build extremely tweaked ASM routines. Hobbysts like us, can only code on the famous 3am coding sessions.
- BTW, most of the game contests on the MSX are related to the MSX1 platform. Few games for the MSX Turbo-R which is a 16 bit computer, and I bet none of those tweaked it even close to it's limits.
And finally skurk, you're right. No one is probably doing this for the money. I would do it for personal satisfaction of winning a contest. IF I ever remember how to code in 68k asm...