With respect to "sister sites," don't forget FlyerTalk which has wonderful info on airlines, hotels, car rental, and destinations.
I find that most sites focus on Caribbean instead of the multitudes of cruise destinations. The other thing lacking is a "truth police" with regard to those items that are not opinions; e.g., cabin size, crew size, itineraries, etc. Also, none of the cruise websites have a good way of rating ships and cruiselines; most methodologies allow for "stuffing" the ballot box and "dissing" the competition. I would like to see someone set up a better way of rating ships online (if I had a suggestion, I would surely offer it).
Finally, what is really missing from the web is accurate "bottom line" pricing information.