I can see how it is overrated, but only really when you consider game length too. They are kind of interchangeable(you'd have to combine them to calculate the ultimate game length). I mean these things matter if you consider pricing, but price rarely ever matters to me(and matters much less to everyone 6+ months after release).
I will say this, if game makes me replay it because of the mechanics(scoring helps, so does a lack of credit feeding), then that is a good fucking game. Arcade games and relatively modern games like Bayonetta, Ninja Gaiden, Godhand, and Vanquish can make me do this.
Adding more content to the game is cool too. Like alternate modes, challenges, or mechanics, but ultimately, what matters most are how well designed the mechanics are. A lot of times extra content is just boring as hell. Like Collect-a-thons or checking boxes through grinding. (e.g. Assassin's Creed, Batman Arkham Asylum)
On the other hand some games are simply designed to be played once and are enjoyable romps for that. (e.g. Ghost Trick/puzzle games, Uncharted/cinematic games) I will say that I usually consider "cinematic" games inferior almost always. (at least some of them have the benefit of being multiplayer-inclusive.)
EDIT: I bet this post is a mess, but fuck it, I am going to sleep.