It was OK. It has an interesting mood to it. It feels kinda set in the 1970s except for the technology like cell phones and modern cars (except the bad guys' cars are older cars!). Granite City felt like RoboCop's Detroit.
I too saw the "twist" coming from the opening monologue, but I'm not sure we are supposed to be fooled. Sure they play dramatic music when Stallone shouts "I am the bad guy!" but that could just be the drama of the reveal to Cyrus and Sam (who do not know what the audience knows), highlighting their reactions.
I did want more background on what happened between him and his brother, both before and during their final fight. Like, what really was the beef between them? I got they had more of a difference over their approach, like Superman vs Batman. Speaking of Batman, I got a real The Dark Knight Rises Bane vibe from Cyrus' wearing a fur-lined leather jacket and mask, giving a speech to the citizens.
And what did Nemesis (the original) think would happen if he lured his brother into a trap to fight, after he had made a hammer that could seriously hurt him? The last minute "oh I don't really want you to die" decision seems to come out of the blue.
I did love the move where he leaps over the car, pulling it on its side to block the explosion.