Hello silver, and welcome to cruise-chat;
there are really only two basic 7 day cruises. The "inside passage" cruises are round trip from either Vancouver or Seattle. The others go across the Gulf of Alaska from Vancouver to Whittier or the reverse.
The ports are pretty much the same for all cruise lines, with slight variations; Ketchikan, Juneau, Skagway, Sitka, Victoria, B.C., Glacier Bay or Tracy Arm (scenic views or glaciers).
Some of the "must see" things are the White Pass Railroad in Skagway, whale watching and/or Mendenhall Glacier in Juneau and hiking or fishing in Ketchikan.
Any of the major cruise lines are good--it just depends on your personal preferences. A travel agent that specializes in cruising can help you with your choice. My favorite is Princess.
Whichever way you go, you will have an extraordinary vacation.
We are here to help if you have other questions.