Hi Gents,
Another great cast!
The debate about the size of Optimus Prime relative to the other bots is interesting, but OP was definitely shown as taller than the other bots throughout the series.
Now of course sizes varied from episode to episode which can sort of throw off this argument:
Yay consistency.
But as mentioned per the size chart they were supposed to follow for the cartoon it's correct Most come up to about his crotch:
Also from a realistic stand point, the size difference between a car and a semi makes sense to produce bots sized differently like that.
Here's a few other Shots showing some of the relative sizes of characters:
Here's a few pics from the first 2 episodes of G1 that show a good comprison with the Arc Bots (I captured this from the a video):
Of course take that as you will as based on the perspective (optimus closer to the camera) there' a shot of sideswipe as he walks in front of him that would lead you to believe sideswipe is both wider, and taller than OP.