Riven/YMMV

Better on DVD: The digital version is much smoother than the original version, which came on a whopping five CD-ROM's that required you to swap them every time you went to another of Riven's five islands. In fact, Riven was one of the earliest PC games to receive a DVD release for this reason.
Even Better Sequel
Quicksand Box: The other games are divided into discrete, self-contained ages which can be completed independently of each other. Riven is almost completely comprised of a single, gigantic age, and it can be frustratingly easy to lose track of everything you have or haven't done yet.
Squick: Gehn captures frogs and smokes frog extract for his pipe.
That One Puzzle: The marble puzzle, sometimes given the Fan Nickname "the waffle iron from Hell." It's extremely tedious to solve, as not only do you have to pinpoint every dome on a hard-to-see 3D map of each island, you also have to physically go to each of those domes, look at the switch that opens them, have a very close eye on which symbol is yellow (they strobe by very quick), then match that symbol to a corresponding color in another room way far and off, then place that corresponding colored marble where it corresponds to map-wise on the waffle iron. To figure all of this out at once is incredibly unintuitive, but the amount of trekking you have to do just to piece together all the right information to get one marble is insane, let alone five! Oh, and if you're playing the original five-disc release, that also means the game brings out the worst of the disc swapping during this puzzle. The game's plot almost completely stops dead in its tracks when you hit this part, and is widely considered the worst part of what is otherwise an Even Better Sequel.