The higher returns come with higher risk of losing the money.
Don't chase past performance. Last year's huge gain in stocks is by no means guaranteed over the next 1-3 years while you are growing your nest egg.
Read "A Random Walk Down Wall Street" if you want to understand more about how risk works with returns.
This might help you as well.
http://www.daveramsey.com/new/baby-steps/
For a short term investment, you need to have your money as liquid as possible, which guarantees the principal a bit more but does have a lower return.
Just keep saving. Also you should have 3-6 months of living expenses saved BEFORE you buy a house. Also budget 1% of the cost of the house for YEARLY maintenance, furniture, and upkeep. (Appliances, yard, etc.)