The concept of a meta-score isn't a new one, but in gaming it can make sense. The bad part so far has been implementation. You can play Dead or Aliuve Xtreme 2 and never see the full 1000 points, but play a game of Avatar and have the full 1000 in under 2 minutes.
If these things had been governed better, they'd be much more relevant. As they are now, they're more or less a nuisance. I have a pretty okay gamerscore (I s'pose), but I'm a completionist, so I was always shooting for 100% in the games I play going back to 486 PCs. This feeds my completionist nature, but also attempts to exploit it (such as with online achievements).
The worst part though are that game companies actually use these things to pad out the value of their games, meaning you'll spend less time enjoying the game and more time grinding for that 1000 head-shots or 40 ranked multiplayer wins.
Kinda makes me miss the old days.