That's a question usually limited to "ship junkies" who argue that the boxy superstructure and shallow draft of modern vessels defines them as cruise ships, while real ocean liners (insert a sigh here) were sleek in appearance with a deep draft. Notice the "were" in that sentence--like I said this is normally a discussion among ship junkies, amateur or otherwise.
So, it came as something of a surprise to see the debate in, of all places, The Daily Echo (a Gannett newspaper in the UK), which reports, "Some quarters have questioned whether Queen Victoria should be classed as either a liner or a cruise ship but the company's president and managing director Carol Marlow is definite on the subject. 'Cunard Line ships do not sail on cruises, Cunard liners sail on voyages,' she said."
The paper seems to solve the riddle by stating, "It seems then that Queen Victoria is something of a hybrid. She will be taking her passengers on fabulous cruises but her hull has been strengthened to allow her to make transatlantic voyages thus giving her liner status." However, comments by readers go back and forth on the issue.
In any case, there are some excellent images of Queen Victoria's Southampton arrival in a photo gallery on the site. Just follow that link if you aren't interested in the "controversy." I'm no expert on ocean liners, but I'll let you know my opinion after I've been on board for a couple nights.