Even though it departed pretty far from the original RE series, it's still a fantastic game worth playing!
Unlike previous games, you are not fighting zombies, but rather Ganados. They are similar to zombies, but smarter, faster and a bit more human like. They also have the ability to communicate between them. The plot is also a little less complicated, and cheesy, but since this game breaks away from the original RE story anyway, it doesn't matter to much. Another new aspect is the ability to purchase and upgrade weapons from a merchant who pops up in the strangest of places.
RE4 also features some great voice acting, nice music that keeps true to the surroundings, and dead on sound FXs combined with the immersive gameplay. It has some well designed, despite easy, puzzles. Best of all, is the boss fights and varieties of Ganados you will face, including insects with the ability to turn invisible, a blind one with incredible hearing and massive steal claws, and an awesome boss fight against Krauser, with some cool little mid-action commands to press. The downside is the all to easy final boss and the lack of the ability to start on pro mode. The graphics also aren't as spiffy as the cube version, but this is compensated by some new modes added to the already existing ones. You will find 3 new types of gameplay, including Seperate Ways (a "second story" that follows Ada), Project Ada (a five level mini-game) and the Mercanaries (a challenging series of mini-games that allow you to unlock new characters including Krauser, Ada, Hunk and Wesker).
There is no multi-player mode though, something i've been hoping a main Resident Evil game would include, but there is still a large amount of replayability, having personally played through the game several times. It's really worth checking out. 9.7/10!
Fan of the Resident Evil series or not, RE4 is a must by for all gamers.