(Site won't let me post this as a "Review", so I figured I'd just put it here for now.)
Stop me if you've heard this one:
A group of people stranded in or on a building,mall,hospital, and/or island fighting off hordes of zombies, occasionally foraging outside of their safe zone to find food,medicine, other survivors, and/or a cure for whatever infection is causing said zombies. Also, there exists a small group of individuals with the genetic resistance that prevents them from turning. Finally, throw in shadowy government agency who caused or are taking advantage of the outbreak for military reasons.
There's nothing new in Dead Island Riptide that would set it apart from the original, it's the same basic story as the original, people need to hole up in one location after another that provides a pocket area of safety while 1-4 people set out to obtain goods or information that will help them survive or, ideally, escape. Most of the art assets are pulled directly from the original, and you get all 4 original playable characters, in addition to one more. There is still weapons degradation, which would be as annoying as ever if it were not for a healthy increase in the number of workbenches strewn around the island that you can stop at on a regular basis to patch up your Lightning Slash Electrical Katana of Doomslaying. Money becomes a non-issue fairly quickly, especially when you realize you can loot a room full of luggage loaded with cash, leave that room, go back, and it's usually all there there again. Also, health seem to be more readily available on Palanai than they were on Banoi, so much so that I ended the game with over 30 unused kits. There are a ton of weapons mods again, from meat bombs to mods that cause area-of-effect fire damage. Everything from the original game is here structure wise, just with more of it.
Why would or should you ever bother playing Riptide? Well, if you didn't enjoy the original, there's nothing here that's going to bring you running back to drop $40-$50 for. It's still pretty janky, and in single player, there are a few choke points where you will find death often, which can be pretty costly (I lost over $17k in a single death at one point). The combat is the same, so if you didn't enjoy the game's fighting style, then that's not going to win you over this time either. The story uses most of the same tired tropes from the original, and manages to add a few more.
Having said all of this, if you are a fan of the combat, like I am, there's a lot of it here. New monsters to fight, a ton of new weapons and weapon mods to enjoy and try out, more island to explore, some pretty neat underground locations. There are also "floaters, which are zombies that lay on top of the water until you get right up on them, then jump at you, maybe scaring the crap out of you the first time it happens, but then just putting you in the habit of smacking any floating body in water with your weapons just to make sure it's not a zombie.
There are also boats this time. Boats with turbo boost. If you run out of boost, there's a better chance of a zombie climbing aboard with you and bringing your love boat to a quick stop. They're also required for hauling certain larger items from remote locations to wherever your current base is, so they do come in handy from time to time, as does the map when it comes time to make your way from one end of the island to the other, since there are numerous dead ends to get caught up in, and the turning radius on your standard island watercraft leaves something to be desired when there are half a dozen infected bearing down on you.
All in all, Riptide is probably only going to appeal for people who had a great love for the original game. There's not a lot of streamlining in the game play, and for all intent, the game looks and plays identically to the first one. I am one of those people, though, having put almost 100 hours into the original, and already around 35 hours into Riptide. Jumping back into the Dead Island universe was a joy, from breaking a Thug's arms with a sledgehammer that is electrified to slicing up a group of zombies with a sword that's set on fire, it's pure fun for me, better than Left4Dead, better than Resident Evil, both series which I tend to enjoy more than I should.
So...3 stars for me, as always, opinions will vary.