Yes, in a just world Bush and Cheney would be tried, found guilty, and then executed for their monstrous war crimes from 2000 - 2008. Not the least of which involved a massive loss of life in Iraq and our military, and a wholesale looting of our nation's treasury to support their war contractor buddies. But the world is not just.
Bush and Cheney, et al. started the Iraq War under false pretenses using trumped up and faulty intelligence with the intention of enriching defense contracting companies (namely Halliburton which, not coincidentally, was headed by Cheney before he became Vice President) and other private American corporations. The administration sent Colin Powell to the United Nations to lie about Iraq's capability to obtain and use weapons of mass destruction. In the ensuing war hundreds of thousands of innocent Iraqi civilians were killed and millions more displaced, and no legitimate proof has ever been given that Iraq posed any threat to the safety or welfare of the United States. In this way the Bush administration violated the Geneva Conventions and should be put on trial for their crimes.
I do think that both Bush and Cheney should be tried for war crimes; Cheney more than bush though, because he really was the mastermind behind the disastrous Bush administration. If you measure the policies Bush ran on and compare them to Cheney's ideas and what actually happened, you will see why.
No Bush and Cheney should not be put on trial for war crimes. They may not have made the best decisions while in office but they did not technically do anything wrong or breach their power. They should not be held accountable for anything that happened during their time in office.
Bush and Cheney were the leaders of the US during a war time and, while people were very much against the war, people forget the intense public support around the war in 2003. The Iraq war is a complicated and nuanced issue that will not be fully understood for many years.