Resident Evil 5 is the latest incarnation of the Resident Evil series, returning to the general storyline of Resident Evil 1-3 but borrowing heavily from the gameplay of Resident Evil 4. In some ways, this formula is successful; in other ways, it isn't. RE5 follows Chris Redfield (from the original) and his new partner Sheva Alomar as they track down a bio-weapons dealer in Africa. They soon discover that the town they are investigating has been infected with a virus, and the inhabitants have become aggressive and homicidal.
Most of the gameplay elements have been carried over from Resident Evil 4. The view is a third-person (or, really, second-person) camera angle, directly over the shoulder of the playable character. Shooting involves using a laser pointer attached to the character's gun; the characters cannot move and shoot at the same time. The two main changes from RE4 are the addition of a partner and a revamped inventory system. The former makes the game into a co-op experience (either local or online, though single player has the partner controlled by the computer), and RE5 features many puzzles that require one person to stay behind and man a console or crank while the other goes ahead and unlocks the door blocking their way. However, for the most part, co-op simply translates to having two characters to shoot at enemies.
Compared to RE4, the game seems to also have more aggressive and numerous enemies primarily due to its cooperative nature. The average villager has attacks similar to RE4's (striking with weapons or grappling), but their attacks are swifter than their previous-game counterparts. When being grappled, the player can either attempt to break free (by waggling the control sticks) or call their partner to come rescue them. If a character is injured to the point of near-death, they limp around until their partner can come and either heal them with an item or inject them with a weak (but free) adrenaline boost.
As a whole, Resident Evil 5 feels free to throw a larger number of enemies at you, including gun-wielding enemies in later chapters. This makes it feel much more like an action game than a survival horror game; there is little reason to run past enemies when defeating them is comparatively easy, and ammo is plentiful.
The cooperative system also ties into the new inventory system; each character has nine slots to hold ammo, guns, grenades, healing items, and so on. Unlike RE4, where items took up relative space based on their size, the size restrictions in RE5 are much more strict. A gun takes up one slot, but so does a healing herb. Characters can swap items if necessary, but are unable to put an item down and pick it back up again. This is one of the few attempts to make the game seem more like "survival horror", rather than simply an action game.
Between chapters, the player has access to a store at which they may sell treasures or items and buy or upgrade weapons. RE5's weapon choice is fairly broad, but unlike RE4, where each weapon filled a particular niche, RE5's weapons don't have much difference besides appearances and general class (machine gun, handgun, rifle, etc).
The graphics and sound are both well-done. Character modeling is well-done and environments are fairly detailed. The design of the new bio-weapons is fairly boring, with the usual array of "mutant dog" "mutant bug" and so on that's permeated Resident Evil since the beginning. Voice acting is good, though this varies from character to character. The music is decent, but not great.
RE5's main problems have to do with the increased action of the series in contrast with the fairly slow control scheme. The lack of peripheral vision - moreso than RE4 - means that it's bizarrely easy to get attacked from behind, and sound cues offer very little to make up for this. This isn't too bad when with a partner, but in the game's extra solo mode, it's absolutely maddening. Another problem with the game is that, due to the nature of its co-op gameplay, segments feel short and broken-up. This is necessary for online play, but interrupts the flow of the gameplay.
Finally, the AI-controlled partner is usually decent, but the player has almost no control over it apart from setting it to either "cover" or "attack" mode. In the former, the partner will use their pistol until they are out of ammo and heal the player character if the player character takes even a slight amount of damage. In the latter, the partner will use their "good" guns and hold off on healing the player, but will also run off into dangerous situations. However, it's fairly obvious by the amount of co-op methods available that the game is meant to be played with another human.
As a whole, RE5 is pretty good - it's fun, but not too deep. It's not quite as good, atmospherically or technically, as RE4, but the co-op tends to make it more fun despite some frustrations.