in no specific order, these are the elements that concur in making a game a good game in my book:
- Good dialogue/grammar. I am not an English native speaker, and I understand that many devs aren't either, but I'd rather play the game in another language I know, than play it in choppy English with terrible sentence structure or straight up wrong translations. It takes me right out of the game immersion if I have to struggle to keep up with the narration. I would even go as far as offer to translate and/or proofread, if the game is otherwise good enough.
-An actual plot that has some merit to it, and ideally also a bit of occasional humour in the dialogues... I have giggled aloud at the occasional 4th wall breaking in a couple of games... and enjoy it when there are games interspread with some humour (I am thinking of for instance Personal Trainer).
-Decent to good graphics (animations being a nice plus, but not an absolute must)... I am a fan of 3d graphics in the genre/style of The adventurous couple. (basically I've consumed enough manga and anime and even hentai for me to rarely be interested in games in that graphic style... though there have been a couple of exceptions if they present particular plotlines or kinks)...
-Playability... only entomologists like bugs. Having a nice finished product with good transitions and as few as possible unnecessary clicks is a nice touch (if it takes me 4 or more clicks to go home to "finish for the day", or maybe reach the map to go from one place to the next, and I MUST do it routinely, then please, give me a "home/map button" shortcut).
Grinding is nice against a woman..not as a way to get through a game. I don't mind it always and there are games in which grinding actually has a purpose and kinda "works" (like treasures of Nadia), but more often than not, tasks and longwinded grindfests and repetitions are added in for padding and don't actually add anything to the game after the initial payload to the first "grind".
-Clearly stated objectives or game mechanics that don't make you wander the map aimlessly waiting to bump into the next plot point or clue as to how to proceed, if need be, a "guide" that will help you along the way (this may just me being lazy but we're not talking elders scrolls here... the production value of these games is rarely so high that it's just a pleasure to walk around and enjoy the scenery like it can be in, say, Skyrim).
-Variation in situations and kinks, and the presence of either unusual kinks or at least some of the ones that I enjoy... Ideally "non standard" sexual activities should be framed within the individual character's personality/sexual "identity" or even be a plot point... and not be just plonked in there as a possibility out of nowhere. Likewise, I understand the logic of progression (peeking, then touching leading up to handjob, to titjob, to bj, to sex)..but if it is repeated identically for every character in the game, it is just bad/lazy writing.. the progression is unnatural and forced half the times, better to have variations of it or dispense with it altogether.
A game that gets high marks on all of the above would be absolutely legendary, but I find that this would be setting the bar way too high, and would actually detract from the enjoyment of other games.. so I don't mind only one or a few of these aspects being fully "there".
A decent balance of these aspects makes for a great game, but it really depends on my mood whether I am looking to explore something more depraved, whether I am in it for the story or something else.
In general, a good story will peak my interest and get me invested in the characters even if the graphic side of things is less well executed, even if there is a lot of text to read, but there are also times that a very well designed game can "tide me over" even with a rather flimsy story that's there just as a generic framework to tie together different kinks.
On the whole, I might play through just about anything that isn't too unplayable, bugged, unintelligible or ugly, but I am definitely partial to good storytelling over too outlandish and jarringly unbelievable situations (I like a good harem as much as the next guy, but if the harem is composed of girls with strong personalities and jealousy who find out about one another, I expect there to be consequences in the game, not "oh well..they're all magically ok with it")... and if the MC is an absolute moron/loser/idiot and utterly unlikeable, then there's no reason that every girl in the game should fall for him unless the plot justifies this in a believable way and not just because of magic dick powers.
I do like the more cerebral games that explore the psyche, the relationships and the motivations behind choosing to pursue an NPC, and for her to go along with it, other than because she's in the game and the MC has a big dick. Again, I don't mind that, but it does get repetitive and I do like a bit more substance to a story.
On average, I prefer Renpy over other formats, but that is not an absolute,... and I don't mind there to be different paths that are mutually exclusive, but in that case, the completionist/kinkster in me would like there to be a way to also see the alternate path or the content I missed out on (something like an extra content feature?)
I guess I should learn to summarize.
Tl;Dr A good game is a balanced effort that takes playability, graphics, plot and context into consideration, with a variety of kinks to spice it up.