There are enough screenshots of Fallout 4 out there in the wild now that Nukeclears was able to get a bunch of them and compare them to similar shots from Fallout 3.
They're not exact comparisons, but they're pretty close. Close enough for you to nod your head, remember Fallout 3 came out in 2008, and think "yup this looks about right".
Fallout 3 is on the left, Fallout 4 on the right. To engage the magic sliders, click on the white arrows and drag.