Yes you can make 2d games
There is nothing to import graphcis from flash unless you can export them to a bitmap format that the XNA FX content pipeline understands. See list here http://msdn2.microsoft.com/en-us/library/bb197848.aspx
Flash graphics are in general vector graphics so won't work well in their native format. You will also need to do a lot more programming in XNA GS than you would in flash as there is no UI for making animations or timelines.
The ZBuffer - News and information for XNA and Managed DirectX
