The 7th Guest is a really old game, and highly nostalgic for me. I remember watching my grandmother play this game- and telling me to get out of the office when a certain scene was played. ;)
Overall, the game has NOT aged well. While the game was graphically advanced when it was first released, nowadays it looks terrible in comparison to more recent releases, primarily due to the FMVs used throughout. One good point, despite the outdated graphics, is that the environment as a whole is pretty well fleshed out. All the rooms of the mansion were unique, creating different atmospheres.
Gameplay-wise, it is slow and clunky. The protaganist walks incredibly slowly, and talks far more often then he likely should. This wouldn't be a problem, if the game gave more hints as to where you should go next - as it is, it's a lot more likely that you'll wander around slowly and aimlessly until you accidently find the next cinematic and puzzle.
The puzzles themselves are either obnoxiously easy, obnoxiously hard, or luck-based - there is even a puzzle that if the randomizer doesn't like you, the puzzle is unsolvable and you need to reset it, possibly several times over before it'll let you solve it.
Story-wise, this game is...special. The story actually doesn't make much sense overall, and due to the poor quality of the FMV, it can be difficult keeping track of the story and what is actually happening. There's a character that actually is never explained as far as I could see, though her presence was likely meant to be a badly placed hint.
Overall, this game is great for the dose of nostalgia - outside of that, though, I'd only recommend this if you really, really like puzzles.