There is no voice recognition system that is completely accurately, and there probably won't be for a long time. Siri definitely isn't the most advanced voice recognition system, but it and Google Voice are the most popular. Siri has got many problems, that's why it's in still in BETA. Also the other problem with Siri is that some of the main features don't work anywhere except America, such as business listings.
News is Google is coming out with a new voice recognition system which will be a lot more advanced than Siri, called Majel. We've still got a while to wait though.