The definitive answer to this is, of course, on
www.cruisecritic.com where the forums have much discussion, and information, on the subject. My personal experience is this:
I'm sailing in a few weeks on Holland America. Though it's my first time with them, they are clear that you can bring on all the wine, soft drinks and water you wish. NO hard liquor. I have purchase a beverage card that saves a little money and will buy as many drinks as the card will cover.
My last three cruises were on Regent Seven Seas. Their three ships are all-inclusive. That means you can bring on all the booze you want because it saves them money as they charge you for NOTHING on board. Wine flows freely and there is an open bar throughout the ship. They even stock a bar with your choice of liquor in most cabins, greet you with a bottle of bubbly and stock a fridge with beer, soda, water or whatever else you desire. It's a more expensive cruise than most of the others, but you also get free air, hotel, shore tours and no tipping to anyone at any time.
Another upcoming cruise is on Crystal, which is going all inclusive this year, so more free booze. These luxury lines seem expensive but, if you upgrade to a suite on a mass market line and pay for tips, drinks, soda, specialty restuarants, shore tours, airfare, etc, it's not that much more.