Why are the 747-8 engines placed differently than on the older versions?
On the 747-8 the engines are heavier and mounted farther ahead of the wing. This results in a torsion moment which reduces the incidence of the wing. As a result, even the unloaded wing will have a lower incidence than that of the older 747-200.



Boeing 747-346 of Transaero (picture source). Note that the engines are no longer tilted up (and consequently the wing tip is tilted leading edge down). The lift force twists the wing such that the incidence in flight is lower than when unloaded and on the ground, especially when the high-lift devices are extended.

Also please make sure to read @Lilibete's answer. I don't know who thought it appropriate to downvote it - it contains another reason for the change in inlet angles, namely the difference in avoidance strategies for foreign object damage.