Final answer:
The density of the universe and the predictability of element abundances are two major lines of evidence that alternative models have not successfully explained like the Big Bang theory.
Step-by-step explanation:
Two major lines of evidence that alternative models have not successfully explained like the Big Bang theory are the density of the universe and the predictability of element abundances. The standard Big Bang model does not explain why the density of the universe is so close to the critical density, which is necessary for the formation of galaxies. Additionally, the model correctly predicts the abundances of the light elements, providing further evidence for its accuracy.