@Fluffy Otters: That's the problem with all counters. The Pokemon they want to counter can just switch out. Under your logic, people shoudn't have counters because they can just switch out.
The deal is whether that counter is useful in wider situations, and whether it is able to take advantage of the turns it forces enemies out.
For instance, in Gen 4, Venusaur could switch in and counter just about any bulky water set-- any Swampert, Vaporeon, or Suicune. Despite this, Venusaur was almost nowhere in OU, while bulky waters were prolific. Why wasn't Venusaur used? Why were Celebi and Shaymin only mid-level OU pokemon at their very best, while bulky waters kept usage equal to over a fourth of the OU metagame? Because Grass was largely useless in the face of the rest of the metagame (with Heatran and other steels everywhere) and had no real way to take advantage of the turns it forced a bulky water type out.
On the other hand, Nattorei succeeded where other bulky grass types failed in past games. Why? Because Spikes and Stealth Rock give it ways to ensure it produces results, and gains your team real advantage every time it comes in.
That is what makes having a counter competitive or not.
Jirachi can switch into and force out many enemies with Ice Punch-- but then what? What does it do to progress the team? What does it do to harm the enemy team? With Nattorei everywhere, Scarf Rachi coming in to spam Iron Head or Ice Punch will hurt itself more than the enemy more often than not! Add Wobb and Zone to the mix, and you have a pokemon that faces even bigger problems than the aforementioned venusaur example.
Also, the same 252 atk / 252 spe Scarf Rachi can only switch into Latios' Draco Meteor and force it out
once. Now you want to talk about Rayquaza?
