Great addition to the series, adds plenty of new stuff, but doesn't feel like a RE sometimes
RE 4 has an interesting plot, great character development and action-packed gameplay. While you're not fighting zombies anymore, the new enemies can be the same deadly. The game is pretty huge too and the PS2 version includes bonus material that expand the game's life even further.
The graphics are top-notch, so are the sound effects and music. Controls are responsive as always and a few good additions are enough to say that this game has the best controls than any other RE game.
The game adds many new things to the RE world, The inventory has changed, there are merchants that sell stuff, the camera follows the player and the action is non-stop, even during the cinemas where you have to use your reflexes at times you don't expect. However, I have to say that at certain moments I felt I was playing a different game, not a continuation of this series. All the changes somehow take away from the classic formula. Also, there are very few horror moments, when other games like RE2 were full of them.
Overall, this is an excellent game and every gamer should have this experience at least once.