I'm going to try address all of these products in point form and then sum up one general point I think encapsulates the whole problem with Sony's business model.
1.The PSP Go- A lot of good ideas that time has come quite yet as the market isn't ready for yet(digital only handheld). The large internal hard drive and ability to use flash cards should been put into the Vita. Price was too high.
2.PS Move- Didn't bring anything new to the table unlike Kinect did. Price was too high.
3.PS3- Other then the high price launch price, not much to say.
4.Xperia- Didn't get the quality games it should have. Price was too high.
5.PS Vita- The launch price was too high, the inability to use non-Sony memory cards, lack of 3rd party support and the poor quality of some of the portable versions of console games.
So what is the common thing here? The price of each product is one factor in why it had trouble selling. PS1 and 2 had a good price point compared to all these products. The PS1 and 2 also weren't the high point of graphics during their generation and yet won those generations in sales, so maybe Sony needs to put their development into other aspects of the system design.