Plantinga is certainly worthy of the award and indeed, some of his fellow philosophers have thought it was long overdue. One of his more recent accomplishments has been his argument that there is a serious conflict between naturalism and evolution, but that theism actually supports evolution or is compatible with it.
The article at the link offers a brief summary of Plantinga's argument:
In contrast to the common claim that evolution is incompatible with theism, the EAAN (Evolutionary Argument Against Naturalism) asserts that evolution is incompatible with naturalism. In standard evolutionary theory, traits of organisms are selected for because they facilitate survival and reproduction.Plantinga is probably most famous for the revolution he wrought in philosophical epistemology with his trilogy of books defending the proposition that belief in God is rational and justified apart from evidence. It is, in other words, a properly basic belief, like one's belief that other people have minds, that one has free will, or that one is experiencing the color red. One is justified in holding these beliefs until confronted with a compelling defeater for them. In the same way, one is rationally justified in believing in God, if one does, in lieu of a compelling defeater for that belief. If no such defeater can be adduced one's theistic belief is perfectly rational.
Plantinga shows that belief forming capacities can be perfectly adaptive even when the beliefs that they generate are false. As a result, if the only explanation for the formation of our belief forming capacities are random trait variation and natural selection, then it is unlikely that belief forming capacities are truth conducive (since there are many more ways to have false-but-adaptive beliefs than there are true beliefs). But it is incoherent to affirm that one’s beliefs are most likely false. As a result, it is incoherent to affirm evolution and naturalism and thus one must surrender one of these beliefs.
In his 2011 book, Where the Conflict Really Lies: Science, Religion, and Naturalism, he challenged the militant atheism and materialism that he found in the sciences. He argued that the real conflict is not between science and religion but between theism and naturalism – theism supports science while naturalism undermines it.
This may not seem like such an extraordinary argument (although it took three books to establish it), but it was ground-breaking back in the 1970s and 80s when many philosophers simply assumed that theistic belief was irrational.
There's much more at the link on Plantinga, his life, work, and the Templeton prize.
