A cruise is great value at the moment. If you have not already tried it then I would thoroughly recommend it. As you say, there are a huge number of options. It really does depends on what you want out of it though.
Our first two cruises were with Thomson. The first was to Norway, the second around the Baltic. The first one was good but the Baltic one at 12 days was one of our most enjoyable holidays ever as you get to see so much in the time available with lots of great ports of call. Thomson also give you a full day at each port which many companies do not.
Last Autumn we travelled on the Queen Mary 2 to New York. The ship is stunning and there are some great deals including a BA or Virgin flight back plus a few days in NY as well. However you do need to be prepared to dress up a bit as Cunard is quite formal in that respect.
We have just booked another 7 night Thomson cruise around the Adriatic in May from Corfu which calls at Venice, Dubrovnik and other ports. http://www.thomson.co.uk/cruise.html
Thomson aren't as posh as Cunard which means that the one optional formal night involves just a jacket and tie. Their ships are older and smaller than the main cruise companies which in many respects is an advantage as the whole experience is quite relaxed and very good value for money plus the quality of food and entertainment is every bit as good as Cunard. You don't need to worry abouit tips either as they are included in the price. If you haven't cruised before then Thomson offer a really good laid back experience. Your wife will absolutely love it and so will you.
Any questions, just PM me.