Anonymous2: This is actually psuedo-addressed by te movie--is game came out while there were still graphical limitations, so he's only really 9 ft tall in comparison with the rest of the humans in the game (who are supposedly regularly sized humans).
Anonymous3: Ralph is 9 feet tall in his own game, but it's an older 8-bit game so its scale is smaller due to the low resolution. Hero's Duty is a modern game on a larger scale, so Ralph is only around the same height as Calhoun there (6-ish feet).
he's nine feet tall, for god's sake
Or something like that.