Well, a cruise is a nice way to see Alaska, but, of course, there is much you miss. I think that all the cruise lines offer cruise/tour packages, so you can see the ports, but also Denali, White Pass, etc. They are expensive, but what a great experience to be able to go on one of those!
Another good (and much less expensive) way to experience Alaska is through Michener's epic novel "Alaska". I read it before we went on the Inside Passage cruise. It really helped me appreciate more what I was seeing. The history of Alaska, especially the period of Russian colonization, is so interesting to me.
After you have read "Alaska", I guarantee, you will HAVE to experience it for yourself someday.