Maybe I'm just too picky in my old age. But if there's one thing that's most commonly known for putting me off a game purchase - without even trying the demo - it's seeing a bunch of reviews refer to the plot, writing, or dialog as lackluster. "Okay game, but mediocre writing... fun combat but really lame story..."
This is a particular problem in adventure games, which are now something of a niche, produced mostly by just-above-amateur enthusiasts or by developers from foreign lands whose English is a bit shaky. A lot of them focus on puzzles. And a lot of adventure players want puzzles. But I want story, and so every time a review for a new adventure comes out and mentions that the story and the characters are pretty weak, I sigh and write another game off my list of things to try.
Same for budget RPGs. The plot tends to be the LAST thing they consider important.
Now, this doesn't really mean I'll never play them. You've seen me going through Titan Quest and not even bothering to read the dialog blocks half the time. But what it does mean is that I tend not to buy these games at full price. I bought Titan Quest off ebay cheap. I'm considering getting one of those game subscription services, which will contain a lot of adventures and RPGs that I wouldn't have bought new because they were kind of lame, but don't mind playing cheap.