I mean, to me, a five star review is for award-winning stuff: "This movie deserved its Best Picture Oscar!" or "This book is a future classic of its genre and will be on recommended reading lists in decades to come."
Conversely, a one star book better have hit the wall on the far side of the room at least once before I finished it...assuming I gritted it out 'til the end in the first place, and a one star movie should be too wretched even for MST3K to roast; utterly devoid of redeeming qualities.
Heck, in my personal rating system it's an unusually good author who can maintain four star quality across any kind of lengthy output. Staying in my genre-fiction bailiwick, even Pratchett or Bujold occasionally phoned in a three star contractual obligations novel.
Three stars is where the bulk of entertainment lives anyway; the movie you watch or the book you read only once, feel you've gotten your money's worth, but don't really feel any need to revisit in the future. Two stars is the bad stuff that you steer people away from.
