But the thing is that the modern market is completely different, you can't realy compare, back then the norm was that a sequel consecutively brings less money, aside from James Bond, which was an anomaly and very episodic, letting it be as successful as it was, it was pretty much a larger version of what the Tarzan films before were doing, running for as long as they could and maintaining their grosses, 007 did that on a larger scale.
If back in the 80s the market was like this, i'm pretty sure films Rambo would have gone past III, instead of getting decades of hiatus. Long story short, the market is very different now, people want to see their heroes and stories continue, something that has drastically increased throughout the 2000s, so it's obvious that you don't have much to compare. Spider-Man shot itself in the foot once it was rebooted, dropping the things the audience loved (Director, the running story, actors, etc), the Marvel films are a different beast, the best comparison are probably Harry Potter and Pirates of the Caribbean, and Pirates is barely milking the brand power it currently has, unlike Transformers, which is smart enough to keep going in full swing, i actualy applaud them for that.
No, the thing is that Rocky is a different character in a different situation, unlike Rambo, he isn't used to killing people, and the people around him would react in a different way. I'm not sure that if the Autobots were in a life or death situation in the middle of the war, them counting how many decepticon they kill would be that bad, it's not as if they were taking pleasure in ripping faces off, though yeah, LotR does take war and death for laughs sometimes.
Either way, with Bay it's all about context too, i think the way he does what he does with Autobots like Optimus Prime, where everyone talks as if he was this holy leader, then when his comrades are fighting he doesn't even try to stop it, doesn't quite work, however, in something like The Rock it does due to the position the characters are in or are pushed into.
Even in war, there are some things you can't do, Optimus kills various oponents he could have instead taken for interrogation, Sentinel's plan had been ended, the guys was on his knees and had no reason to fight any longer. To be honest, the story in TF3 between Optimus and Sentinel had potential, but once again i feel like it was completely wasted in its execution, that moment could have had more weight and we may not have been discussing it here if that were the case.
As i said with Wolverine, it's a different type of hero, he's an anti-hero, we know not everything he does is completely correct, but we cheer for him because we know his history well, just like with a guy such as Harry Calaham, James Bond or the Man with no name, these are no goodie-goodies, they have sins and they know so.
I don't think the bots have been properly used since the first film, there you had the excuse that they needed to be introduced through a kid's eyes, and for now were a bit interchangeable, you also had one Autobot that was completely wasted (was it Jazz?), but on the whole it was acceptable for the first film, even Starscream showed himself to be a badass, giving two autobots a run for their money, then in the sequels they have barely been developed, with Megatron getting ever less threatening.