I was looking at overall career as of now and I agree that PPG should decrease as you age, but I figured it was close to a fair comparison as you can get since Datsyuk would have benefited more from higher scoring years from a league perspective combined with Toews theoretically not getting benefit from his prime years yet.
As I said before though...I do think Toews gets far more credit than he should, but only because he seems to be rated so high by many. The only hesitation I have is that the players seem to give him quite a bit of respect as well (e.g. Crosby having to call him before accepting Team Canada Captaincy). To me, he's more like a Bergeron type player (which is a very good player of course, but not the best in the world).