The SNES port of Doom was powered with the SuperFX chip, which was a 3D accelerator capable of generating polygons and otherwise rendering a picture like what mike was saying. The SNES's VRAM, DMA capabilities and SuperFX chip way outperforms the Neo Geo in a Doom-like application.
The SNES "Mode 7 chip" is just one of several video modes built into the S-PPU cores (there are two of them in the original SNES). The Mode 7 "aka Landscape effect" is very limited on stock SNES hardware, the DSP1 co-processor was put in some cartridges to make the Mode 7 functionality more effective.
You could in theory put a fast CPU and some RAM onto the CHA board in a Neo Geo game to pre-render the image for a Doom game, but that wouldn't be particularly amazing. the problem as Mike put it is the Neo Geo is really only good at filling a screen with tons of 2D graphics in a somewhat limited fashion. What it's not good at is software rendering. It's something the Genesis and SNES can do, but not the Neo Geo.
Now what the Neo Geo would be REALLY good at is a point n click adventure game, LucasArts-style.
Well, I am impressed with your vast knowledge of the Neo Hardware.
I will totally admit, I know very little about the hardware itself, and how it works, so all I can do is tell you what SNK told me, and just take their word for it, and then hear what you have to say and take your word for it. The only thing I can think of is that the Neo-Geo, having vastly superior cartridge sizes, and having two boards, one for graphics and one for sound, I believe that if people put their imagination and their knowledge of how this stuff works, to work for them, there could be a LOT of things added to the Neo-Geo Cartridges, and even to the motherboards as well, that can add to the already amazing stuff that the Neo-Geo can pull off when done correctly.
For example, I have had in my mind, for years and years, that there could be a Neo-Geo modem attachment made for the system that can go in between the cart and the system, that would add super fast modem capabilities, that would allow the system to connect to the internet so we can then dial in our friends phone numbers after turning the machine on, and if they are playing the same game at the same time using the same device, and in a "now waiting" mode, we can play games two or 4 player like done in Emulators that do something similar for online play. It's just a matter of using your imagination, putting knowledge to work, and making the product. With todays technology and internet speeds it should be feasable, and yet nobody is making such an amazing product, so we are stuck with the crap Emulation and online support of the Neo-Geo Station on PS3.
I think if people put their collective knowledge to work on this amazing system, upgrade boards similar to the "Mode 7" chip can be made for a Neo-Geo in the future, thus adding new technology to this dated machine, and breathing new life into it, and it would make the gaming experience on it unlike anything we have EVER seen in the past. I really think it's not a matter of how, but more of a matter of when and getting people to stop thinking that we "can't do it", and reversing that type of thinking to "we can do it, we just need to find out HOW to do it", and putting that to work. Only then, will we be able to see more amazing stuff on this "King of the Monsters" of a console be optimized.
I might totally be wrong, but, we will never know until we attempt to do it, and that is the problem, is that nobody has even attempted to do it yet on the Neo-Geo.
The Future Is Now, and the future is ours, if we just try new things that nobody has tried before. Sadly, my lack of how the AES/MVS is what holds me back on making new and innovative products for it, for if I knew how this beast worked, I would be making the best stuff for it that my mind could conceive.
-J