You might be out of luck if you do not have the originals, as you know now the 2010 was compressing the pictures.
Just to clarify that happens before or after you save the PP presentation
First save the picture to hard drive and open it with something like iPhoto.
If you like the quality there we can continue.
If you do not like the quality it is the end of the road, no advanced settings will help here.
You could report the picture file size here, like is it in 500k- 1Meg, or more or less than 100k.
In second case your only option is to keep the picture size as small as possible to retain the quality (resolution).