Mervissa, please see a cruise-oriented travel agent! There is so much to choose from, and though I might have some good suggestions, but in order for you to find just the right cruise, you'll need to talk with someone and let them know more detail of what you are looking for. Sounds like you may want one of the newer ships, as they have a lot to offer, and many are just beautiful, but if you have a classic ocean liner in mind, aim for Queen Mary 2.
One thing for sure - stay away from the 2-night cruise lines!!