Resident Evil 4 marked a huge departure for the survival horror series, as it redefined so many elements of Capcom's classic games. Resident Evil 5 takes RE4's best elements and adapts them to the buddy system. Co-op is all the rage these days, and RE5 refines once-revolutionary gameplay to make it palatable for two. In that sense, this new sequel breaks little ground, but still serves as a satisfying horror experience.
The action picks up a decade after the first title. Chris Redfield now works as an agent at BSAA, a security conglomerate that combats bioterrorism. He's in the fictitious African nation Kikuju, trying to stop the spread of a virus when, naturally, things go completely awry. West African BSAA agent Sheva Alomar starts out as Chris's local guide, but soon ends up fighting alongside him to fend off swarms of infected villagers and horrific mutations. Eventually, they discover that the roots of the infection are deeper than they seem.
Whether you're playing alone or with a friend, RE5 is an action-packed, nerve-racking rollercoaster ride. In single-player, you'll step into Chris' shoes, and an AI-controlled Sheva fights alongside you. In co-op, the host plays as Chris, and the second player takes on Sheva's role. It's important to delineate the difference between the single-player and co-op experience, since plenty of people will play a solo game at least once.
In my single-player run, I experienced fewer problems with the AI-controlled Sheva than I had with, say, Dom in Gears of War 2. She never stole a cover point or sorely-needed ammo. Plus, you have control over how much she goes on the offensive, or how conservatively she attacks. Since she holds the same amount of inventory as Chris, you can save a few health or ammo slots by safekeeping items with her. Think of her as a companion who matches your skills, every step of the way.
Although AI-controlled Sheva's mostly a great help, she can become a bit of a hindrance toward the end of the game. During a few big showdowns in the last chapter she stood away from a cover point and left herself susceptible to huge damage. Sometimes, she'll follow you around when all you want to do is flank a pack of infected foot soldiers. In the epic finale, she can be downright irritating to deal with. Sometimes, you just wish you could position her someplace specific, but that's not really an option.