It was a fun gimmick for about a year, which for me was 2007-2008.
I don't have the time or interest to dig through everybody else's gamerscores on individual games, and a cumulative gamerscore says more about how many games you buy than it does about how good you are at them. The only platinum I ever got was FF7 OG, and that's because I cheated my way through Emerald and Ruby Weapons and used a guide to get Barrett at the Gold Saucer.
I'm too busy actually enjoying the games.