This song's great, not only because adam lambert sang it, but also because of the reality it tells us through its lyrics.
The meaning of this song is when the world goes on in a routine, it's going to be a "mad world." This song tells of the sad events continuously going on as not directly stated in the lines "daily races, going nowhere, going nowhere."
The song then provokes those who will hear it to start making a change, to make this world better. It makes the listener realize what the world's situation is. :)
Hope this meaning helps you understand more the song and take a deep thought about it. Vote up if you liked the meaning. Thanks, God bless. :)