The most common cancers affecting humankind are (in order):
For men: prostate cancer (most don't die from it, but die with it), lung cancer, colo-rectal cancer.
For women: lung cancer, breast cancer, colo-rectal cancer
Overall, cancers of the prostate, the breast, the lung, and the colon and rectum -- in that order -- have the highest incidence among the U.S. population.
These figures are for the U.S. and probably are totally different in undeveloped countries.