Summary first: If you own a GameCube, get ED. When the game first came out in June, I wasn't too interested; it sounded pretty cheesy and the concept sounded difficult to pull off, especially for Nintendo. However, after playing completely trough the game, I can honestly say this is one of the most engrossing, atmospheric games ever.
The graphics are pretty good, nothing out of this world, but certainly not a hindrance. The one thing that really sets this game apart is the story. For the first few hours, it seems pointless and disjointed, but as the game winds down, the pieces come together and create the best story ever told in a video game. I'm serious--no video game has ever used so many characters in so many different ways to get to the conclusion.
I won't go into the point, goal, etc., but over the course of the game, you will play as several (8-10) different characters, all connected to the Roivas family during different time eras. One of the coolest parts is that you will play in the same location several times, but several hundred years apart as a different character under different circumstances. The level is vaguely familiar, but time has changed it completely and it's eerie enough to give you goosebumps.
This sounds totally ridiculous, but playing this game in the dark makes it much better. Resident Evil can be frightening at times, but ED is the first game to ever make me jump in my chair. The game can get very creepy and playing in the dark really enhances the experience. The insanity meter is pretty cool, though easily kept at a high level, and some pretty wierd things happen if it gets too low.
Finally, the sound of ED is fantastic. I own all 3 next gen systems and ED, though it has no digital audio connection, is in the Top 5 sounding games to date. I'm a home theater enthusiast and sound is very important to me in rating a game: ED delivers with eerie music/sound effects and very good surround sound.
Aside from Metroid, ED is the best GameCube game available. The comparison to Resident Evil is not a very good one--this is not survival horror, but closer to a freaky Zelda as an adventure game. Do yourself a favor and pick this one up.