I don't know if cult classic is the right word because the general public did seem to like them pretty well at the time. The Transformers fandom outright talked me out of seeing ROTF in theaters until some rando cashier in the real world talked me back into it.
We know Transformers is cool, but I think we've gotten numb to just how cool it is. Imagine walking into the 07 movie not really knowing what a Transformer is, not knowing there's two sides, not knowing how much characterization they should have, just watching that movie slowly lay it all out.