A CS major would probably take about 8 semester-long (or 12 quarter-long) junior/senior level CS courses, plus whatever frosh/soph level CS courses are prerequisites (variable in number due to how different departments organize their curricula).
So it would be desirable if the department frequently offered somewhat more than that number of junior/senior level CS courses, to allow for some flexibility due to student interest. Also important is the breadth of subarea coverage, since some CS departments are heavily skewed toward some subareas while lacking in coverage in others (e.g. Tulane is heavy in theory, computational biology, and artificial intelligence, but limited in other subareas).