Actually there will be some variance depending on your discipline and what you're doing. I think generally to be in proper balance your hip should be directly over your heel. I don't do a lot of western, but I don't know of many situations in the english world when you don't want this leg position.
The upper body is where most of the difference will be. In a full seat (most dressage riders) your upper body should be vertical and yes, your ear/shoulder/hip/heel will be in line. However, at the posting trot your upper body should be slightly in front of the vertical. I think George Morris even says a full 15-20 degrees in front. A hunter, who generally tries to keep their weight over the horse's center of gravity, spends a lot of time up in a half seat/2 point, where your upper body will be tipped forward as well. Imagine a crosscountry rider galloping across an open field with a vertical upper body. Most likely not going to happen. But all these riders should have their hip over their heel.
There is no hard and fast rule about exact positions because a lot of it will depend on a rider's conformation. There is no rule as to exactly how deep a heel must be, but with people who jump the heel must be lower then the toe, must be able to absorb shock. With a dressage rider I think they are more level with their feet (like the picture you posted). A dressage rider and a jumper uses their leg/seat/heel differently so naturally the "correct" position will be different.
The best way to know what correct position should be is to understand *why* it's important to be in that position.