It's pretty clear that Al-Qaeda etc accomplished at least some of their goals. The 9/11 attack drew the US into Afghanistan and Iraq. And chaos in Iraq has been a huge factor in the growth of ISIS. 9/11 has also corroded respect for the US Constitution. The CIA got into torture, and the NSA maxed out its intercept and analysis capabilities.

So yes, it "sadly looks like the terrorists have won" :(

Edit: Deleted "('just a piece of paper' according to W)".