The Saboteur's side missions (blowing up German strongholds) takes a LOOOOOOOONG time.
But the campaign for the game is awesome, very interesting story and a great protagonist.
If you complete The Saboteurs campaign within a week your looking at a possible 800G's (with a quick look at a guide to get some of the novelty achievements)
Lastly, use your perks on vehicles (much better than having to ride all 30 vehicles, especially as it's unclear which ones you have driven or not)
Dead Space will also net you a good GS week, i would play a combination of them both to be honest (neither have high TA now, so just rack up a big score)










