Although others talked about evolution and natural selection before he did, his work was what made the ideas enter our collective consciousness, changing forever our views of science and life. Aside from his detailed scientific work to reveal the workings of natural laws, Darwin was able to write in an engaging way. What’s most evident in those writings is that he revered life, yet saw in death the possibilities for renewal.
The last paragraph of On the origin of species is worth quoting again on this, his birthday:
It is interesting to contemplate an entangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent on each other in so complex a manner, have all been produced by laws acting around us…
Thus, from the war of nature, from famine and death, the most exalted object which we are capable of conceiving, namely, the production of the higher animals, directly follows. There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.
See the references for interesting stories about Darwin and the evolution of his own ideas and texts.
Darwin, Charles R. (1859). On the origin of species. Various publishers and editions; the link here and the quote are for the 1st edition, in Project Gutenberg.
Urbanowicz, Charles F. (2002). There is a grandeur In this view of life. In Amanda Chesworth et al. (eds.), Darwin Day collection one: The best single idea ever. Albuquerque, New Mexico: Tangled Bank. See also the full version: On Darwin: Countdown to 2008 / 2009!