Dead Island is a great game, even thought it has it's flaws...
There is, also, a good character upgrade system in this game, and it forces you to choose carefully how you spend your XP points, since your decision to upgrade your character in a way can change how the game plays. The skill trees have lots of variety that adds value to the game.
There are lots of different types of zombies and some areas encourage you to play them in co-op, since they can be really challenging while playing solo. There is a 4 player co-op option with the possibility of dropping inn/out at any time. It's a really fun addition to the game!
It's fun to use all sort of weapons and you can even combine different "junk" and create interesting, more powerful, weapons to use on the zombies. You will not fight only zombies though, there are survivals that will try to take advantage of the zombie apocalypse and will try to kill you. This is the part where you will need to use guns; and it's also the week part of the game.
The survivals AI is awful. they will stop all of a sudden and shoot straight at you, almost begging for the bullet to the head. However they will attack usually in big numbers, and each shot will take a lot of damage from your character. But guns are the week part of the game. Another problem with the game is the story. It is extremaly weak, and there is an awful plot that doesn't make any sense. The voice acting is also bad.
The rest is great; beautiful landscape, impressive melee game play, and 20 hrs. to enjoy in this game means a lot.
Good:
+ Melee combat
+ Beautiful landscapes
+ Lots to do
Bad:
- Human AI
- Story
- Voice acting