Really? Are there not games with big 2D sprites on them for the 3do? Those sprites are only a little bigger than the 16 bit versions.
You're forgetting there is still a lot of frames of animation in those small sprites (which the 16-bit and
32X versions mostly lack). Your comparison of RAM with the other contemporary platforms (PS1, Saturn) is kind of moot as well. What kind of RAM does each system have? Is the 3DO's exactly the same? What about other technical aspects? Processor type? Bus speeds? Other chips and processors to take into account? An operating system that the platform has to run in the background that eats up precious memory (which the other contemporaries didn't have to do, but the 3DO did)? There is a lot to take into account.
Anyway, I don't really know how the specs of the platforms compare asides from basic numbers on paper (which mean little, most likely). Purely going by what I have seen on the 3DO (Samurai Shodown probably being the most impressive/technically capable fighting game with its scrolling, scaling and large characters), I doubt Primal Rage could have been done full justice. Even SS is choppy in nature (I only mean that objectively, as few 3DO titles actually run at 60FPS, let alone a solid/constant 30FPS; most are lower, including SS). Way of the Warrior is another example that is technically sound, and it never runs at a consistent framerate (not a consistently good one anyway). Keeping that in mind, and seeing how Primal Rage runs in its current form on 3DO, it's highly doubtful we ever would have gotten a better version of Primal Rage, and based on other fighters for the system, it's highly possible it wouldn't have been able to get much better without sacrificing performance stability and playability.