The financial crisis is the fault of many parties, going back decades. It is really the end result of Lyndon Johnson's capitulation to Wall Street with regards to the Vietnam War. Kennedy, under the advice of 5-star generals Dwight D. Eisenhower and Douglas Macarthur, refused to engage the United States in a land war in Asia. Well, duh.
Long story short, Johnson engaged the United States in a land war in Asia. This so destroyed the US economy that we went to net negative levels of growth in terms of productive capacity and basic economic infrastructure in about 1967-68. In other words, our industrial and infrastructure capital began wearing out at a rate faster than it was being replaced.
In turn, this led to the collapse of Bretton Woods, the world's financial system at the time, in 1971. Since then, the world has been operating under a Venetian-style monetarist financial system, which - unlike the Bretton Woods system, which required settlement in a physical commodity (gold) - has no basis in reality. The usury of this Venetian-style system has made long term capital investment exceedingly difficult, resulting in an ongoing infrastructure collapse in most parts of the world. Thus, the productive potential of most of the world's population, in terms of basic physical output, has been declining for decades. Correspondingly, living standards for most of the lower 80-90% of the world's family income earners has been declining over this time.
Here in the US, we covered up the collapse in physical productivity by creating an expanding level of debt and financial obligations. This resulted in an accelerating rate of looting of the physical economy, in order to prop up a bankrupt financial system. What liars call the "subprime bubble" was deliberately created for purposes of debt farming, so as to keep the bubble of the bankrupt financial system expanding. If you pay attention, you notice that is bubble was by no means restricted to the subprime region of the mortgage market; in fact, the leverage in the commercial real estate market is far greater. During this time, in order to facilitate expansion of the bubble, the Federal Reserve has fed the Wall Street money center banks a steadily increasing supply of monetary aggregates.
So, now we're at the point in which physical production has collapsed to such an extreme extent that it's obvious that most of the quadrillions of dollars in claims on physical output (the financial aggregates) can never be satisfied. Thus, the world is hopelessly bankrupt. What we must do now is enter into a process of national bankruptcy reorganization, whereby we sort out the debts, wipe out all of the claims which have no relation to physical economic activity, and then authorize sovereign credit to rebuilt the real economy. These dynamics can be compiled into a visual pedagogical device, which I shall link to below. It really explains itself.
Now, as I previously pointed out, every President since Nixon has been complicit in this. So no, it's not entirely Bush's fault, although since he went with the fraudulent "bailout" policy rather than reorganization when the final collapse phase began, he's more guilty than most. However, I would still lay the biggest blame at the feet of Alan Greenspan and Larry Summers.