javihyuga: Because a "doesn't work on Windows 7 x64" is quite more useful than four long paragraphs about how much fun someone had with the game when he was 7 years old.
Except that -- to use your "doesn't work on Windows 7 x64" example -- often the problem has more to do with that specific user's system than with Windows 7 overall (especially if GOG has tested the game on 7 and decided to support it on that version of Windows). One user saying it doesn't work on a certain OS can stop others for whom it would work from buying and enjoying it, because someone thought, "If my system can't run it, then NO ONE'S can!" So this might save people from spending money on a game that wouldn't work for them, but it might also scare people away who wouldn't have had any problems.
The "reviews" of this sort I really have a problem with are the ones that just say something like the example you gave, or "Tried to install, but nthing happened. this sucks, dont but it!", and NOTHING ELSE! If you're going to be foolish enough to write a 'bug report' review that you can't edit or remove after the fact (as opposed to filing a proper Support ticket),
at least include more detail. ...Scratch that -- just contact Support, use the forums, whatever. ;)
When it comes to technical problems with a game, by all means, mention bugs encountered in the game, mention poor performance, mention wrong-sounding music emulation, frequent save corruption, these sorts of things. If you never got the game to run in the first place, though, you are not qualified to
review the game, any more than someone who
would've bought it if only it weren't so darned expensive is qualified to do so.