Let's see; mine would be:
* Baldur's Gate - captured the feeling of the tabletop game better
than almost any other
* Planescape - great story, slightly weak in the gameplay, excellent
soundtrack
* Pool of Radiance - while dated compared to modern games, it was
revolutionary at the time.
* Neverwinter Nights - not so much for the gameplay of the core game,
but for the framework that allowed so many excellent mods
* Eye of the Beholder - not a personal favorite, but still a well-made
game that helped revitalize interest in the franchise
* Shadow over Mystara/Tower of Doom - a feature-packed brawler that
inexplicably also managed to captured the essence of D&D
Also, special mention to
* Stronghold: The D&D Kingdom Simulator - not a great game by any
means, but one I quite enjoyed playing
Now... as for the worst? That's much harder.
Slayer? Pirates of Realmspace? Daggerdale? Iron & Blood? There are so
many stinkers to choose from!