I feel like cheating can ruin the anticipation of scenes, but it really depends on the theme of the game. For me a large part of a game's appeal is in not knowing what a scene will be like until it happens. I'm seemingly one of the few enjoyers of game over sex lol. But I would say my desire to cheat is sort of proportional to the vibe I get from a game. The grindier it is relative to the shortness/level of bad writing in scenes, the more likely I am to be like 'well, this is terrible, I wonder if this game does
anything good?' Sometimes I find the impetus to cheat comes mainly from finding the scenes I've already found to be disappointing at best, so I end up no longer excited to find out what hot scene will happen if I do <ill-advised thing>.
However if the game seems fun and relevant to my interests, and maintains a solid level of writing, I'll usually try to play fairly to the game's expectations. Like, if losing everything you worked hard for to seduction/madness/etc, like in a lot of works containing level or stat draining, seems like an intended theme of a game, I'll try to play those fairly to experience that theme. It's kind of hard to care about your stats if you can make them whatever you want to be, right?
Galleries are kind of a different bag, and are mostly about being able to
replay a given scene, I think. Obvs some people will want to avoid gameplay entirely (just go read a porn novel, seriously) and skip to a gallery, but I feel you either need some form of gallery/time travel mechanic, or a way to repeat scenes in the main gameplay. Otherwise what I find happens to me is I drop saves every five seconds in case there's an unrepeatable scene, which ends up amounting to a self-made, badly-labelled gallery feature by the time I'm done with a game.
So I think the extent that galleries ruin a game is going to depend on some level how important the wider context is to those scenes, and how much the viewer wants to just see pretty pictures/animations. If it's something heavily tied into, say, stats (or the loss thereof) in an RPG, or a long, heavy buildup of flirting in a VN, then it's going to hit differently than if you watch it in a gallery without having experienced that context.
I would definitely say I'm not above cheating when something seems too boring, and I'm really not one of those people to complain about grind typically. It's more a sense of whether the game's systems
feel boring to me, like... oh, an example would be my visceral hatred of Succubus Covenant. That game had
horrendously slow, tedious, criminally uninspired combat that I tried desperately to discuss with its creator, and disappointing writing for scenes, so that would be a great example of a game I would have cheated to see the gallery of in a heartbeat, were the gallery in that game actually functional
