I played this game back when it came out after being totally enamored by Resident Evil 2, and I remember being sorely disappointed. The difference - in terms of graphics, sound, atmosphere, and overall coolness - between RE1 and RE2 was so astonishing, that this game just seemed like one of those sell-out moves where they plaster over a good game with a new plot. I mean, the door animations are the same, the zombies look the same, the weapons are the same (though it is cool that in easy mode you get all the weapons from the start). I played it through the police station and gave up.
Then, after being totally enamored (again) by Resident Evil 4, I decided I'd pick this one up and try it again. I was pleasantly surprised. The graphics look very dated, but not too distracting. And yes, a lot of the stuff is recycled from RE2, but there are also a lot of nice changes: There are fat zombies, zombies in suits, and zombies that move reasonably fast. Also, once you get past the police station, there are some nice exteriors, walking around the abandoned city; it's nice you don't get caught up inside a single building for most of the game, like in RE1 and 2. The background are well-rendered, the characters are as one-dimensional as you'd expect from a RE game, but the voice acting is slightly above average (and I get a kick out of hearing Jean Grey's voice from the old X-Men cartoon as Jill). Stuff like the ability to dodge monsters is welcome, and the quick turn (now standard in GameCube RE games) was a nice addition.
And there's Nemesis. A cool villain, tough to beat, shows up over and over and over again, almost to the point of annoying, but not quite. He's a little like a mixture of the man in the coat and William Birkin from RE2 - tough to kill, ever-mutating, etc.
Many people discredit this game for being a worthless side-story. It does seem like a quick cash-in between the superior RE2 and Code Veronica, but it does a nice job of closing off the Raccoon City storyline (and fleshing out the Umbrella conspiracy). It also provides the plot for the movie Resident Evil Apocalypse, so if you enjoyed that movie (either as a movie or as a hilarious piece of 21st-century techno-kitsch), I'd recommend this one. Not stellar, but it's better than I expected it to be, and definitely not a "collector's-only" title.