I really liked this film. I think the OP forgot to mention the great role Harry Connick Jr. had. I liked Copycat better than Seven. Seven had that great atmosphere and the shocking ending, but I thought it was boring. Copycat grabbed me right from jump.
I do agree though that the Copycat serial killer wasn't as good as Spacey. His method or killing style wasn't as creative either. That being said, I thought the Copycat guy had a cool motivation.
Despite the solid performances I guess Copycat just wasn't able to stand out enough. Though after Silence of the Lambs I think serial killers became in vogue so maybe people just saw it as just another serial killer film to add to the list of films and TV shows that featured them.