There is something wrong with yours so I suggest you get it checked out. From your avatar it looks like you have a facelift model? If so then it runs on a Sanden SD7V16 compressor and these are pretty efficient. The earlier cars use a different compressor which doesn't seem to be quite so good.
I've got a facelift and my aircon works very well and within a 5 minutes of it being switched on my car is like a fridge
One thing that is worth checking are the rubber hoses that run to the compressor (front left of the car as looking into the engine bay). These are very close to the exhaust manifold and there are a few cases where they have actually melted and all the gas has escaped through the hole.
Another possible issue is that if there is little gas in the system of the aircon has hardly ever been used then the seals inside the system harden and go brittle. This is because the gas actually contains the lubrication needed by the seals. With damaged/brittle seals, the performance will be seriously impacted. If you have aircon in the car you need to ensure you use it regularly to keep the seals properly lubricated.