The PCE Hu-card limitation is probably 256MB limit, if done correctly. If we compared the SNES carts, to the PCE HU, and was released simutameously, they would match up. I mean all the post MMX games after the first one, up till, X5.
We are thinking about limitation, but most of the effects in 2d videogames are programmed effects, not just sprite, or background overlapping. The voice, and audio waves could be stored as with TOPSNES, and video data could run as well, but most likely will be shorter.
Lets not think about the limitations of the past, however, lets think about the abundance, ( and cheapness ) of the future.