What is good to me may not be so for you. Don't pick a cruise because Dave said it was great. Select an itinerary that you like and then look at the ships which do that itinerary, or an itinerary that is close. Then look at opinions.
First time cruisers really should find a cruise specialist to help them. I've seen too many first timers who saw an advertisement that enticed them, and then they went on-line or to a 1-800 number and booked something that ended up not being what they had hoped for. And please note that I am not bashing the people who work for on-line cruise agencies. But if you aren't asked questions about your interests, your expectations, your hobbies, etc., before a cruise booking is mentioned, then you need to hang up or close your web brower.