I'll respectfully disagree :). It has redeeming qualities but the game is crap compared to other dungeon crawlers, like Ultima Underworld (years ahead of its time and still not bad by any means while Stonekeep had a legendary dev cycle and didn't hold up even when it came out, let alone today).

Like others have said, it's a matter of taste, but I think price does play a big role on people leaving a review or not. You buy a new, very hyped, expensive game and it turns out to be a turd. You rate it poorly and give it poor reviews in order to prevent others from making the same mistake you made. You buy a cheap old game and it turns out to be a turd. You buy something else and move on, it was just 6 bucks and there's nothing really new to say about it.
Only if you really hated the game, only if it brought you grief, does one usually takes the time to warn others about the grief potential a game has and how it can turn playing the game into a bad experience, but when the game is average and you didn't like it but didn't hate it either... it doesn't really merit spending your time making a review.
Meta critic or gamerankings have reviews for many of the games here from the time they came out, though sometimes you'll see they knock off points because the game was buggy on release or the graphics look old. GOGers aren't exactly picky on graphics and the games on GOG are released with the latest patches, so some points of the reviews may not apply.

I seem rate games depending on how fun it is play now (since I have played none of the older games on here before as I was too young to do so) but I'm not sure if everyone does this. Like Outcast for example, none of the reviews mention how slow it is (apart from one).

AlDepth, welcome to the boards and GOG. It is true there are some games rated higher then you or I might do so, but it is all subjective, so people that loved the game back when will likely still love the game presently.
I think AndrewC made a good point about "Rose colored glasses and all."
Anyway, the games you remember well and fondly you will likely be buying as well.
Just remember to write a good and glowing review! ;o)

Nostalgia goggles.
Also, generally speaking, most of the games here are...well, good.

I don't see this as a problem. One of the great things about GoG that I've noticed so far is that I can pop into the forum for a game I haven't purchased yet and see what folks are saying there. It may turn out I find out a nit more than what the reviews said on closer inspection and I base my judgment on that. I love the fact that a real community of old gamers is growing and if we keep sharing input it can only get better!

Just an observation on reviews and scores (and not just on GOG) ...No matter what the score is read the review; many times glowing score will also mention the pitfalls of the game.
Frankly, with gog games have many pitfalls because UI and control styles have changed much since they came out; simple things that were once intuitive now are not because we are so used the shock of the new. Simple things like complete quest logging just aren't always there; I was playing one game from gog (can't remember which one) and when I clicked on the quest info it game me nothing. I thought to myself - "holy crap - you mean I have to write down quest info when I am told "and then remembered what it use to be like. Modern games have frankly made me lazy and I just have gotten out of the habit of writing things down. Also, I have noticed modern games have made me intellilectually lazy - as well. So I sometimes have to put on my old-school hat to play. Many old school games also take a long time to get into - you just can't pick them up and expect a positive immediate reward and you are expected to have read the manual (or at least skimmed it).
Don't get me wrong I love many games on gog.com, but some old lengendary games can be problematic if you go into the game with a modern gaming mindset.

GOG's games are so cheap that I don't really bother much with them if it turns out I don't immediately like them (instead of trying to play further to "get my money's worth" or whatever). And if I'm to rate or even write a review of a game, I'll want to do so after having enough experience with them to know I'm not getting it wrong. In other words, if I don't enjoy a GOG-release much, it's very unlikely that I will play it enough to feel I have the experience needed to write a proper review.
So were I to review anything on GOG, it'd be a game that I've played a lot and therefore enjoyed a lot, which in turn means I'd pretty much only write positive reviews. The same is probably true for a lot of people, so you'll generally see more positive reviews than negative ones, even in situations where the games in question aren't generally considered all that great to begin with.

Well, i honestly love it, but fair enough, we'll have to agree to disagree on this one ;)

Yep.... I have lots on my list I bought, half of which I've yet to play... but at even 10 bucks... I figure if I can spend 20 bucks on a movie I'll watch once, I can spend half that on a game I may or may not even play.... Eventually I might get around...if not...perhaps someone will tell me how ubarly awesome a game is and i'll try it.
And as for reviews... I go by what the peeps I know say they loved... I mean, I'll respect their opinion... even if I were to hate whatever it was... but... we all have our likes....