The custom graphics hardware in CPS2 and NeoGeo is more advanced than the AGA or ECS, although with a good coder, the Amiga can match those systems with the right amount of RAM, although it would experience slow-down if there were too many sprites on screen.
A game like SFA3 would be possible in 2MB. It might need to lose a few colours and animation frames, just as the Playstation version did, but would still be perfectly playable. Games like Shadow Fighter, Elfmania and Fightin' Spirit all had large sprites, animated or parallax backgrounds, and several moves, and all those games were designed to run on 1MB ECS Amigas (even though AGA versions of two of them were released, they weren't much different to the originals). An AGA Amiga has twice as much RAM, and can handle sprite sizes twice as big as an ECS Amiga.
I'm not sure how well a game like Metal Slug would run, I guess you'd need an Amiga-specific version, like Metal Slug Advance, unless it was loading background blocks and sprites from the CD or hard drive as you progressed through the levels.
