There's a few things wrong with this.
-The Wii has sold 30 million more consoles than either competitor.
-It's limited to 5m+ selling games.
-It makes no mention of games just below this threshold.
I don't think you could draw any really meaningful data from this chart to support your argument. A better chart would be all the million sellers split into category's for each console. Better yet would the cumulative sales of every game in a specific genre per console. Then you could look at the figures in relation to the size of the install base.