Reviews on the store pages are not reliable for review purposes and it's a logical explanation for it. First of all, buying games it's not a lottery for most people. If i love playing turn-based RPGs, i might not go ahead and buy all sport games in order for me to rate them. I'm not a reviewer i am passionate about computer games, but i am passionate about computer games that touch the genres that i enjoy playing. So, just because of that, the rating will move towards being positive from a general user perspective.
Same principle goes for the desire of writing reviews. I don't usually write reviews, and i definitely don't write for games that i find "meh". I'm might write for games that i find good, or for games that i find bad, but not for "meh". And that's the case for many users, so you won't find objectivity, as, again, we're not reviewers, we're gamers.
Now, there is something different going on with Steam, for example. Over there, you will find much more games with bad ratings than on GOG. And there are more reasons for that, but the main one is that there are more releases over there. And i mean games that are launched on Steam and they are played for the first time by people that are buying them over there. So, you will get 1.0 version of the game, and, many of them might have some problems until next patches, or simply being bad. So, you will have those negative reviews flowing for these titles. On GOG, you get mostly older games, that, in many cases, have stand the test of time. They were popular games back in the days, some of them were patched and over-patched, so there are less chances of people complaining about bugs and stuff like that.
As for nostalgia, again, we're gamers. We're allowed to be nostalgic, and we should be allowed to express our nostalgia to other fellow gamers.
I personally rarely read user reviews before purchasing a game. I always prefer reviews written by people that do that for money, as they are more objective. It's their job to be. I suggest you doing the same.