Kinect wouldn't exist. Move probably wouldn't although I guess the Eyetoy was bound to appear again.
Sony would probably have overtaken 360 worldwide sales although I still think 360 would have done as well in US thanks to Live so it would be a close one/two position - I say this as I believe the Wii blocked the PS3's growth a lot more than 360, particularly in EMEAA.
A number of developers would have fallen by the wayside - unable to deliver big enough selling HD titles and with no lower cost environment (apart from PSP/DS) available to them.
Most Mario titles, etc. sell well but obviously Wii Fit, Sports Resorts, etc. wouldn't have sold the same.
The above seem pretty likely to me.
Some maybes...
Sony focus more on PSN / Online and matching 360 differentiators instead of Move
MS focus more on non-English territories and emerging markets instead of Kinect / US homeground
Try to be reasonable... its easier than you think...
