I've taken to caring more about my game ranks on psnprofiles.com more than my actual completion rate. I want to try lots of games and don't want to waste time with hilarious difficult or annoying multiplayer trophies. So I shoot for A rank if I can, but obviously the occasional game I just try out and never play or one that sucks slips in (like NFS Rivals... not impressed at all with that game).
I did change my Mercenary Kings rank to A from F simply by getting one easy gold trophy though. That was funny.