part 1) There were only four well developed robot characters in the original Transformers cartoon. Every other robot was either a plot device or an everyman that could have been replaced with any other robot.
part 2) Only Bumblebee, Starscream, Rodimus Prime and Sky Lynx stood out as unique individuals with personality.
part 3) Megatron and Optimus had stereotypical leader role cardboard cutout personalities and, like the majority of characters in the cartoon, were defined only by their allegiances. Megatron existed only as a reason to get Prime to go out and do heroic things, which were usually just different ways he stopped Megatron.
part 4) Grimlock, Soundwave and Wheelie didn't have character, they had bizarre speech impediments. Never confuse bizarre speech impediments with personalities.