Yes but lets stick within the Arcades. Since violent and Scary games existed in the time period Ralph is from.
It just sounds like the dialog was written by someone who really doesn't play videogames.
"When did videogames get to violent and scary"
Well hmmm let me think... Honestly probably since the NES or if you don't accept that within the SNES (As early as the Atari truthfully)
Also how are you defining "Scary?" Because the original Clocktower which was a 2-bit game was a lot more scary then your weird Metroid/Gears-of-war mix on the best day. What you were playing wasn't scary...
It is just a weird peice of dialog I'd expect a parent to say... Not a videogame character who exists in a world where all videogames exist.
I can only guess it is in there SPECIFICALLY to say what all the non-videogame playing parents are thinking.
I don't mean to turn this into a thing, but you're contradicting yourself. You say "lets stick within the arcades" and then immediately cite NES games for your evidence. I spent a metric shitload of time in the arcades in the 80's. I don't remember anything that was even remotely disturbing or traumatizing. (Okay, maybe the "Game Over" screen from Ninja Gaiden, where you were about to sawed in half by a blade if the timer ran out. But even that was stylized, with the screen just turning red and a little digitized groan to indicate what happened). N.A.R.C. was an exception and it was notable precisely because it was such an aberration of violence in the arcade (and that was in 1988).
The light gun shooters like Operation Wolf were violent but it was a very conventional, non-gory form of violence. Many of your enemies were vehicles rather than individual people, and even when it was actual soldiers, a killing hit just made them crumple into a heap or disappear into an explosion cloud, not burst into gibs. Contrast that with a "modern" arcade shooter like House of the Dead or Area 51.
I'm not saying that the movie SHOULD be preachy about videogame violence (and i'll be pissed if that's a central theme), but I think it's a valid line of dialogue, especially coming from a character who's only known his 8-bit world where nobody actually dies on-screen.