Oh, giant ape, clearly.
The giant ape just has certain advantages, either in the giant ape v. dinosaur arena, or in the giant ape vs. giant robot arena.
First is the ability to grip strength and fine control. Dinosaurs just can't grab onto something like an ape can, they have to rely on more unwieldy forms of bludgeoning combat, which robots can easily avoid. Robots can't be prepared for an ape grabbing it by the arm, and throwing it to the ground, then standing it up, and suplexing it into submission. Heck, the giant ape could probably even atomic suplex the robot if it wanted to.
Second, the ape has the distinct advantage of using outside weapons. Throw a giant pine tree like a spear? Check. Use a boulder to bash the robot in the face? Check. Put two cars on its hands in order to increase its already awesome punching power? Check.
Third, and most importantly, is the giant apes intelligence. If they can teach Koko the gorilla to speak, then I'm guessing Kong (who, I remind you, is also a king and already well versed at fighting dinosaurs) can probably figure out the rudamentary inner workings of your less advanced Giant Robots. Now, if the robot were being controlled from a remote location by a person (a'la Johnny Socko), Kong would have the advantage of instant reaction time, while it would take the humans time to figure out Kong's next move. That and Kong would probably just pick Johnny up and throw him into the side of a building.
Now, if the robot is being piloted by a bunch of spunky teenagers, Kong would simply appeal to their sense of faggy liberal acceptance, and then punch through the hull and eat them.
Basically: Kong is greater than all beasts, metal or not. Honestly, the only things that would have a shot against Kong would be Godzilla, Galactus (but the Silver Surfer would never allow it), or possibly a hoard of Viking berserkers, who also had jetpacks.
However, if this is a giant robot from outer space, and it has hyper-real artificial intelligence, Kong still wins, but on a technicality. More likely: they just team up and destroy the Universe.