From Left-to-right, top-to-bottom, let's call them Pictures A, B, and C.
A and C are taken from similar angles. However, most iterations of this meme have used a different picture for A, which is from the same angle as B.

So I feel the creator of this image is being a bit deceptive. Regardless, A and C are the ones to compare since they are from the same angle. Close inspection shows that the crowd does thin more towards the back of C.This is more apparent in the image that I have posted above due to the angle.
However, people have accused these pictures of being taken at different times, so we should use another method to confirm or disprove crowd size. DC Metro reports that on the day of Trump's inauguration, 570,557 trips were taken. This is lower than either of Obama's inaugurations, 1.1 million in 2009 and 782,000 in 2003. Assuming that metro use is approximately proportional to attendance, this supports the view that Trump's inauguration attendance was lower than Obama's.

By which I mean both Trump ones. Obama's was packed all the way to the Lincoln Memorial. Trump's petters off in both of his pics.