This is about the scene where Simba is running through the desert with the awesome music and chanting in the background. And when my family and I were watching it recently, we, all being runners, start discussing how lions run.
Disney drew lions realistically in The Lion King, so it's safe to assume that they also drew Simba's run as lions run in real life. (And based on videos I saw of real lions running, it is in fact correct). Problem though. For one, lions have a bad ratio of lung/body size. This means that they will run out of blood oxygen, and therefore energy, very fast. Because of this, lions have a poor endurance. Beat one at a sprint (or get a head start) and you can outrun one any day of the weak. And two, they have fur and don't sweat. In Africa, they can over heat very quickly in the mid-day sun. But the most important aspect is the run itself. Lions don't run efficiently. At all. Their entire body moves up and down (fighting gravity more than they need), they have four limbs to provide energy for, and they're heavy.
So this got me thinking. In the desert, there's no water. So Simba had to cross it in less then a drink's fill, and then some because the Pridelands are dried up. So I will give him less then a day in crossing the distance between the jungle and the Pridelands. But lions don't run very fast. And for the most part, Simba would have to walk.
So I reckon that the jungle is very close to the Pridelands. At most, the diameter of the Pridelands away (roughly 10 miles).
By comparison, a fit, well motivated human can cross that distance on foot in about two hours.