-making a 640x480 diablo clone. You could have basic tiles in chipram and apply a mask to make darker or lighter the sections and copy the tiles with the blitter but it would still be a challenge due to the high number of frames from the main characters.
Doing isometric tile scrolling requires transparent blitting ability for the blitter. The blitter has very, VERY poor performance doing transparent blits. We'd need a CPU-blit routine like GameSmith used.
-making a neogeo like fighting game with a decent number of colours fullscreen zooming, animated background, a texture in the floor, parallax scrolls and lots of animations would need decent coding skills. All moving with quarter pixel scrolling, not just the background.
Fullscreen zooming often requires chunky-pixel graphics. Quarter-pixel scrolling requires it be done in low-resolution graphics.
-making a good horizontal scrolling game with lots of parallax, transparency for smoke, big sprites that take the entire screen with animation... with 256colours and/or ham8. And quarter pixel scrolling!
Alpha-blending for fog requires chunky-pixel graphics at the very least (if not hardware accelerated alpha), AGA sprites aren't that wide (only 64-pixels maximum and 16 colors shared between them), parallax requires dual-playfield mode (which limits the display to 15 foreground and 16 background colors), and HAM8 doesn't support horizontal scrolling (if you try it gives you weird color fringes at the edges).
-making strategy games like starcraft run at 640x480 and 256colours/ham8 with smooth scrolling, fog...
I think that coding for >= 16bits requires breaking some limits. 8bit games are quite simpler than >=16bit ones and you can't content yourself making a scroll that would be hard to do on a c64 and saying "oh I have made a scroll that is hard to do on a c64 so my game is done". Making high quality amiga games takes more than a single-pixel scroll with 2 diminute 4-colour sprites jerking at 2 frames.
4-color sprites are more numerous than 16-color sprites. Doing chunky-to-HAM8 requires at least a PowerPC accelerator. Doing 640x480 with sprites requires interlaced sprite support which is not available in AmigaOS 3.9 or earlier.
Almost all of the special effects you have named would work better on a graphics card than on AGA or would require a 500+ MHz PowerPC to implement. IMHO, if you need a 500+ MHz machine to implement those features, you're better off using something other than an Amiga.
