RE5 is not only an excellent new addition to the series, but it's also an amazing co-op experience.
Right from the get-go you'll notice that Resident Evil 5 feels like it's 2005 predecessor but as you progress you'll notice slight differences that really sets the gameplay apart. As I mentioned earlier, you now have a partner to assist you in killing the hordes of Majini that you'll face in the game, along with that partner comes new features. Every now and again you have the option to save or get saved by your partner, help your partner up high ledges, or simply say thanks for the first-aid spray.
There are times when your AI controlled partner really shines, like when you are on the brink of death, Sheva will come to your aid with an herb, she'll cover you while you are reloading, and she'll also grab gold and treasures that you may have missed, other times not so much. The AI will sometimes hog ammo for weapons that she doesn't even own, waste ammo unnecessarily, and walk into traps that a blind man could see, but overall the AI is much better than some others I've encountered.
A wide variety of enemies will keep you on your toes, from bottle wielding Majini to giant spider creatures that eject projectiles from their anus. Enemies have several routes to choose from when attacking, so if you aren't observant of your surroundings, you might find yourself feasting on a chainsaw sandwich. The boss encounters in the game weren't over-the-top difficult but I did have trouble with a few.
The weapons were made for how you like to play. If you enjoy being tactical, consider a rifle, if running right into the action is more your style, a shotgun is your best friend. There's a great variety of different weapon classes to choose from, all of which have at least three or more types to use at your disposal.
With a great assortment of weapons and enemies, a first-rate AI, amazing gameplay mechanics, and a story that ties up loose ends from earlier games but leaves space for a few more games, RE5 is a must have for long time fans of the series and complete newcomers alike.