Theoretically...couldn't the same thing be accomplished with the use of Diplomacy or Intimidate?
I'll just zero in on the 3e/Pathfinder rules here because:
a) previous editions didn't have Diplomacy or Intimidate at all
b) 4e has an extremely limited scope of what Diplomacy and Intimidate can do mechanically
Now, with that settled here is why Charm Person is nothing like either or both of those skills. I will only be discussing what the rules of the game explicitly state that they do because anything else is a pure Mother May I asspull by the DM at which point all discussion of the actual rules becomes meaningless.
Intimidate can do two things. You can use a Standard Action in combat to make a fairly easy DC check and cause one creature to become shaken for one round (or longer in Pathfinder). This is a generic debuff that does not in any way influence the action of the target. Secondly, you can take an entire minute of time to make a similar check to make a creature friendly for a few minutes. This time restriction makes it difficult to use in passing or in combat and even then the things you can force the creature to do are limited.
Diplomacy on the other hand is a decent contender... once you can slap down a +40 or +50 bonus. Diplomancers are well known for destroying games since the DCs for their checks are set in stone more or less and take away the DM's ability to present intelligent NPCs or even enemies or monsters to the players. In Pathfinder Diplomacy loses this ability to instantly befriend a band of orcs in the first round of combat but guess what DOESN'T get a nerf...
Charm Person, lastly, can be used at level 1 and in the middle of combat if needed and contrary to what everyone in this topic has been saying actually DOES allow you to give commands to the charmed person and tell them what to do. Sometimes it requires a paltry charisma check in the case of fighting its own allies, but unless your DM is
cheating then it does exactly what the spell says it does and the creature will do what you say so long as you don't order it to smash it's own head into a wall. Beyond that, Charm Person lasts a whopping 1 hour per level, meaning even a level 1 caster using the spell gets far more mileage out of it than anyone with an infinite diplomacy and intimidate bonus. At very
very worst Charm Person can be used as a combat trick to remove an enemy from a fight. A level 1 save or suck with an unfavorable saving throw bonus. That only unravels a fight. A better usage by far is to gain control over a crucial NPC and unravel the DMs entire plot. At level 1.