I did a forum search, and no one mentioned the Gabriel Knight series.
Gabriel Knight: Sins of the Fathers (henceforth referred to as "GK1") was originally released in 1993 on 12 floppy disks, and again in 1996, this time on CD-ROM plus voice acting.
GK1 is one of the best P&C [Point -and-Click] adventure games I have ever played; the game brilliantly weaved fact and fiction to tell a current-day story about a series of "Voodoo Murders" in New Orleans. The game was intelligent, informative, and VERY fun to play, but the best aspect of this game was the characters. Gabriel Knight is an "author" who owns an almost-bankrupt "rare" bookstore in downtown New Orleans, and sets it upon himself to solve these murders. GK is not perfect: He's kind of a womanizer, and doesn't really think things through. He's joined by Grace Nakimura, his secretary at the store and best friend, though they have their share of often hilarious arguments.
Another one of the best things about GK1 is that, though it is rated "T" by the ESRB, it is by no means a game for kids or perhaps even teens. Aside from the complex and quite mature theme, GK will frequently make sexual comments and swear ("shit"), but on top of that, during the Voodoo Hounfour, there are pixel breasts, and the game expects the player to take it fairly seriously, being an actually mature game, instead of showing naughty bits and swearing for the sake of giggles.
Bonus: In the 1996 CD-ROM version, the voices are done by more than a few famous people, such as Tim Curry, Mark Hamill, Michael Dorn (who was Worf on ST:TNG), and a few others.