Even if you've played every other Resident Evil game out there...you haven't played anything like this one.
RE4 ditches the whole tank-style fixed-camera scheme from previous RE games and uses an extremely simple 3rd person shooter technique. Move with the left stick. Look with the right stick. Aim with R1. Shoot with X. That's it. It's one of the simplest control schemes ever achieved in a game.
In the game you play as Leon S. Kennedy (who seems like a metrosexual at first, a staple in Japanese-produced games), a US Secret Agent who's job is to find the president's daughter somewhere in rural Spain. You find out later she's been kidnapped by a cult who's followers are controlled by a parasite called Las Plagas. They aren't zombies. They're just people who are controlled as puppets by Las Plagas. They communicate and strategize amongst one another. They surround and flank you. RE4 feels more like an action-shooter than survival-horror. The game isn't actually scary, until you encounter enemies called Regenerators or Iron Maidens. When you enter a room they are in, their presence is announced by a loud un-rhythmic breathing. You're thinking, "Oh crap, not one of these again" and you'll find yourself slowly peeking around every corner until you find where it is. On top of that, they're the hardest creatures to kill, and the most dangerous.
The game itself is pretty long. My first run took me 22 hours. The game is designed so well that you'll want to play through it again and beat your last time. On the PS2 version there is also extras such as Assignment Ada and Separate Ways, which add about 6 hours of content.
The graphics are very good, better than most PS2 games. The characters and emvironments are designed realistically and strategically.
The game is a must-own for almost everybody. It's the reason I'm getting Resident Evil 5 as soon as it is released.