On a PC, no matter how much RAM you have, don't get into the idea that you can use it all, because a lot of it is being taken by the operating system and background processes, while on a console, there are not as many background processes and programs.
Also, the processor also plays a big role, not just the amount of RAM you have installed. Once again, on a console, the processor is mostly executing instructions from just the game, while on a PC, it has to execute windows, background processes and services, and other instructions.
This applies to older consoles, but the need for RAM was not very high. Because on conventional PCs, instructions for the processor are stored in RAM, while on a console which uses a ROM cartridge, you can store your 48mbit of instructions and data separately, and the console will read the instructions from the ROM, and RAM can just be used as a place to store temporary things.