Shadow of Destiny

This game is very interesting and the graphics are "drop dead gorgeous". On the downside, you can die and then you have to play the chapter over again. You are also being timed and have to be fast. You should follow a walkthrough to get it done on time. You can put "shadow of destiny walkthrough" in Google. In spite of these drawbacks the game is so interesting I could hardly stop playing.

Myst

Myst games are a bit lonely because you don't interact with people in the game very much. But the first Myst has outstanding puzzles and a very interesting world. The good thing about the first Myst is that the puzzles are challenging but reasonable. You should try to play the whole game without a walkthough. Games are a much better if you figure it out on your own without needing a walkthrough. I got stuck two times in Myst and looked up the answer but the puzzle was legit. It doesn't have nonsense puzzles like some games I played.

Syberia

This game is very interesting and has great puzzles, and you interact with a lot of people (and automatons).  

Sanitarium

This is another very interesting game. The same goes for "Grim Fandango". Both have my walkthroughs on this site. You interact with a lot of people in these games and solve interesting puzzles. They are great adventure games and and a lot of fun.  

Keepsake

This is an interesting game that has it's own help system in the game. You don't really need a walkthough in this one. It's another fun adventure game.

And Then There Were None

This is an Agatha Christie murder mystery. I used a walkthough for most of the game. There are a lot of games like that. I don't know how you are supposed to guess what to do next most of the time. But anyway this one is fun.

Jack the Ripper

This is an interesting game from the Adventure Company. The puzzles aren't that great but the story is, except for the poor ending. You talk to a lot of interesting people. It's not for children. You mostly follow a walkthrough but you can walk around the world and get lucky finding something new, because the world isn't that big. However you need to save the game a lot, because if you don't follow the walkthrough it could jam up or you just can't proceed in the game anymore. It's fun though because the story is great and the graphics are great.

King's Quest V

This was the first adventure game I played and I've been hooked on them since. It was on the old square disks that went in the A drive. You had to save the game a lot because you could die and then hopefully you have a saved game not too far back. An even worse problem was that if you missed picking up an item early in the game you could not finish the game without the needed item. And there was no way to get back to get the item. This outrageous problem has been corrected in games that are not so old. King's Quest VI is also great. King's Quest VIII - Mask of Eternity is great fun, although it has a lot of fighting. Besides the King's Quest games honorable mention also goes to the "Gabriel Knight" and the "Broken Sword" games.