Owning a SNES, Megadrive and Amiga I would have to say that for sheer arcade replication the Megadrive wins.
The 6-Button Megadrive pad was far more true to the cabinets than the shoulder buttons of the SNES (and consoles ever since).
Nothing really comes close to the Streets of Rage and Sonic games for sprite animation, scrolling and multi-channel sound. Shinobi was another good one and Yuzo Koshiro certainly knew how to get the most out of that little Z80 sound processor. Treasure were also a good exploiter of the Sega Megadrive with Gunstar Heroes, Alien Soldier and Dynamite Headdy now appearing on a retro compilation.
On the subject of sound chips, Megadrive's was a 10-channel audio processor so you could say it was more capable than the SNES, particularly when the Mega-CD added it's own 22KHz PCM processor and CDDA. Not to mention the Megadrive/Mega-CD/32X combo.
The SuperFX chip used in some SNES carts was, I believe, just a maths chip. It was used in Starwing(/Starfox), Stunt Race FX and Doom, I don't think it was used in Killer Instinct. KI was a damn fine beat 'em up though, equally as good as Streetighter 2 (I did a 64 hit combo with Orchid once!)
A lot of the speech samples on the Megadrive Streetfighter 2:CE were cracklier than the SNES but alledgedly this was to use more memory for character animation (and boy was it good on Megadrive). Megadrive SF2:CE was 24-MBit which is smaller than the 4x 880K floppies (27½-MBit) the risible Amiga version resided on.
Megadrive Super Streetfighter 2 was 40-MBit (5MB or 6x 880K floppies). There really isn't excuse for anything but perfection on a CD32 version as the 3DO version was apparently pretty good).
As for Zool 2, well the Jaguar version beat the Amiga one hands down. It has the same resolution from what I can make out but the scrolling is fluid (unlike the Zool 2 AGA which is crappy). Also, the Jag version has simultaneous Sound and Music.
Some Amiga games were lazy and there's no excuse for that, US Gold definately deserve infamy for their {bleep}ups. If you want to witness what Amiga can do in terms of sound and scrolling forget Ruff 'N Tumble and try Kid Chaos. I'm not sure if it's AGA but it has scrolling as smoothe and fast as Sonic, the character (A caveman) spins around much the same way and is basically a higher octane Zool.
I heard Super Stardust was crap on PC! It's a damn good game on AGA Amigas machines though, standard Stardust for ECS is just as playable with fantastic eye and ear candy!
I agree about Chaos Engine's scrolling, it's certainly not up to Mercs on Megadrive.
I suppose now all these machines are classed as retro you can pick them up a little cheaper and with good bundles.
Even though I'm a fan of the Sonic games and Zool/Kid Chaos, nothing is more beautiful to the eyes and ears than Donkey Kong Country on SNES.
:banana: :banana: ;-)
EDIT:
I have a 1987 copy of Streetfighter 1 (1x 880k floppy or 7-MBit) but I can't get it to run.
:-(