Folks here have already covered many good points on why RoboCop should not be remade; I'd like to add one of my own-
I personally do not think there is an actor currently active in the business today who could pull off the deeply-detailed performance that Peter Weller gave as Murphy in the first movie. Not only would they have to act the part of a human being who is tormented and brain-wiped at the same time, but would also have to convincingly portray the movements and mannerisms of machine-driven parts and the precise, rigid, mechanical movements characteristic of them. This is physical and demanding; it took Peter Weller some time to get the movements down if memory serves.
Additionally, the original chemistry between several of the characters (both friendships and rivalries) would be almost impossible to replicate, such as the relationship between Murphy and Lewis while Murphy is rediscovering his humanity (I thought the scenes with him and Lewis as he had his helmet off in the factory were poignant and touching), the seething, subdued hatred between Robert Morton and Dick Jones, and the antagonistic clash between Clarence Boddicker and Murphy, both pre and post RoboCop transformation.
Any new film is most likely not going to have any of this, or skew them so badly that it will destroy the point of the story. In the original film, we feel for poor Murphy because of what he lost, and through no fault of his own. Yet, he is a hero: despite all of that, he continues to do his duty even when the police force is after him and he is badly damaged by them. He continues on even when his partner, Lewis, is injured and he himself is critically damaged by Boddicker with a well-placed shot from a makeshift spear. And despite an ED-209 guarding the door and Dick Jones taking the Old Man as hostage, Murphy still presses on to do his job to the end.
In the end, we cheer Murphy for being human, yet being made of a far stronger "mettle" than the alloy his body is now made of. My concern is the "reboot" will not have any of this and simply focus on making RoboCop a springy, fleet-footed, cyber-ninja with a badge. But, i guess we'll have to see...