In standard mode, no I wouldn't say that. Everything looks nice and crisp at usual viewing distances (over 12"). The only time I would really notice it is in Zoomed Display mode. The 6s doesn't look so good in that situation, due to font aliasing. In contrast, the 7+ looks fine in Zoomed Display mode.But honeslty, you can agree with me that your 6S looks pixelated compared to your 7+, right?
It also could be argued that the 6s is more in need of Zoomed Display mode than the 7+, since the default sizing of the fonts of the 6s is smaller than the 7+.
I don't know how it is in games though, since we generally don't use these phones for games.