The main difference, from my point of view is this:
Bush was attacked for conducting said war in a way that would lead to victory. The left/liberals/whatever wailed that he was inhuman and a murderer and so forth.
And how was he going to "lead to victory"? With 4000 dead American troops, a country in shambles, and every single civil or political right erased or under fire in the homeland?
Obama is being attacked because he is trying to fundamentally change the way the US operates internally, never mind what people in Europe think of the situation, I don't like it.
Well, you know, maybe it's time to change. Maybe it's time for the US to get on board with what the rest of the developed world discovered fifty years ago. Unfortunately, we have people still so afflicted with Cold War paranoia and out for blood McCarthy style that we're going to remain the most backwards developed nation for a long long long time.
Bush did many things wrong, I won't deny it, but he didn't try and change the country in a way contrary to her founding.
Which was over 200 years ago. Blacks were slaves. Women couldn't vote. America was a tiny secluded country of thirteen states and not even three million people, most of them WASPs or black slaves. Now it's the sole remaining superpower in the world whose borders stretch from coast to coast with fifty states and well over 300 million people from all different ethnicities and religions. Oh, and nevermind the technological advances.
Despite what most ultraconservatives think, we can't keep living in 1783.