Is also pretty awful (a theatrical advertisement for the new toy line up)
Well, yeah, it was mercenary, and everything on screen was designed to be sold in your local Toys "Ya" Us, but if that's the packed-to-the-rafters-with-imagination result you get from designing a movie around the sale of dolls, we need more movies designed around the sale of dolls.
I also liked the flawed hero. All the characters are sharply drawn, really, except maybe Arcee, but Hot Rod is a real achievement. Not every franchise film is willing to have their new protagonist fuck up and kill your favorite character, and fewer have the ability to pull that off. That's like if C3PO had tripped Han Solo into a bed of spikes, and then they not only went and kept you from wanting C3PO to die, but actually made you want him to win. And even better, they did it so adeptly even little children understood the narrative necessity of their hero's death.
I dunno. Maybe it really is only because it's the first movie I ever saw, but I love the shit out of that film.
Regarding Grimlock, I think they missed their chance with the Fallen. Those guys could've easily been Dinobots--you just shift the "17,000 B.C." to "70 million B.C." I guess they'd have been evil, but Grimlock beyond good and evil, Grimlock is king.