I personally can't regularly 100% a game.
I've completed 4 games to 100% but 2 were arcade games worth only 200 points each; Battlefield 1943 and Portal: Still Alive, one game did have 1000 points but it was spread across 7 achievements so they were each worth like 200+ points; Blazing Angels, and the last one I played was LEGO Star Wars 3 and games of that nature tend to be easy to get 100% completion on.
I've completed 4 games to 100% but 2 were arcade games worth only 200 points each; Battlefield 1943 and Portal: Still Alive, one game did have 1000 points but it was spread across 7 achievements so they were each worth like 200+ points; Blazing Angels, and the last one I played was LEGO Star Wars 3 and games of that nature tend to be easy to get 100% completion on.