You can play Sims 2 on med-low, Sims 3 & Mass Effect 1 on very Low, and not Mass Effect 2 or Oblivion, I think. Sorry, laptops aren't very upgradable. The Intel Integrated graphics just aren't very powerful (aside from new Sandy Bridges which are so-so).
Don't go buying games assuming you can play them though--I might be overestimating your graphics capabilities. Check the Game-o-meter: http://www.yougamers.com/gameometer/10259/