Some brave soul recently sat down to watch "every major press conference" put on by Microsoft and Sony from 2013-2016, then tallied up how many games were shown at each event and how long it was before they publicly came out or cancelled.
The results, posted to Reddit (and partially excerpted below), make for interesting reading, especially as the game industry braces for E3 in Los Angeles next week.
According to this informal survey, Sony showed more games than Microsoft during the 3-year period (400 vs. 160) and those games, on average, were cancelled less (1 percent vs. 3.1 percent) and came out more quickly (11.32 months, on average, vs. Microsoft's average of 13.72).
If you only look at the games shown at each company's E3 event, the time-to-release gap narrows but still remains in Sony's favor -- 13.28 months vs. 13.56.
Of course, all of this data comes with significant caveats. It hasn't been rigorously reviewed (though the person did share a copy of the spreadsheet with data and methodologies used to document their press event binge), it makes some tricky distinctions about which games count as "shown" and when, and it covers a pretty arbitrary time period.
Admittedly, the time required to dig up and watch video game press events would seem to increase exponentially the further back you get; this person noted on Reddit that it took them over a week just to find, watch and document three years of Sony and Microsoft's press events.