I'm probably going to get burned at the stake for some of my opinions, but:
Dark Seed
Played this just the other day and it reminded me of why I hate adventure games. I clicked everything, did everything I thought I could do and even wrote down extensive notes but couldn't solve the game. Finally I looked up a walkthru and found out that I had missed an item that was so small I couldn't freaking SEE it, and also that I had to do things in a totally illogical order (you have to steal the gun after being arrested? WTF?)
I liked the Giger artwork, but on that note I felt like the plot was a waste--what we end up with is typical B-list comic book villains who just happen to be particularly creepy-looking, and I hate it when they waste a plot like that.
System Shock 2
I actually discovered the entire franchise last year and played both games back-to-back. I loved System Shock 1, but System Shock 2 removed everything I liked about the first one and replaced it with lame RPG elements that were simply done wrong and made you feel like your every decision was a mistake. I also didn't like how often enemies respawned and, worse, how they were always right behind you (they respawned in SS1 too, but usually in another part of the level rather than being down your butt all the time), the way it doesn't pause in the inventory or while hacking, and how the plot was so predictable and not as "weird" or "disturbing" as I had heard people claim.
("Yes, we get it, you love being a hive-mind. Now will you shut up about it?")
Silent Hill 2
Sorry, Yahtzee, but I thought this was a huge step down from Silent Hill 1. SH1 was genuinely kind of creepy and had an interesting premise, while SH2 goes and gives you this sob-story about a guy being tortured by his "inner demons" which are being brought to life by this town. I'm sorry but there's something very un-creepy about it all being in the guy's head.