As much as I love early Sierra adventure games, the voice recording and playback is not something that I like that much - crackling noise, break-ups during playing of voices, and sometimes, you can make out the studio "echo", especially in King's Quest V. Even in Gabriel Knight 1, the quality is poor. But that doesn't stop me from playing them again and again and again.
(Of course, one might argue that these games were the early of the earliest batch and voice technology may be rudimentary at best, but still....)
Fate of Atlantis has great music - both OPL3 and MT-32 pieces. The voice seems to play ok, but the volume of speech seems to be recorded at a lower level.
DOTT and Sam n' Max are ok.
Eco Quest has great music and the CD version got good voice overs too. But the CD version is quite rare.
By the time Sound Canvas and GM music came into the mainstream games, the inclusion of full speech was already too obvious, almost leaning towards an obligation to include it.
Many adventure game "enhanced" editions that were remastered and came on CDs included speech that also had MIDI music. In fact, only the classic adventure games can hold claim of having full speech with midi music in them. In other genre, the speech will be more interspersed - either during a cut-scene or a movie or during grunts or affirmation to orders or actions taken by the player.
The advent of CD helped to boost the inclusion of speech in games. But it also slowly killed the MIDI - due to the inclusion of higher quality CD audio tracks.
MIDI, nevertheless, lives on in the hearts of the MIDI aficionados and enthusiasts.
From some of my collection (Other than the games already mentioned) :
1.Quest for Glory IV CD version
2. BioForge
3.System Shock 1 CD Version (Just sold mine a few months back)
4. Freddy Pharkas Frontier Pharmacist CD version
5. The Lost Files of Sherlock Holmes : Case of the Serrated Scalpel - CD Version
6. Fable - adventure game
7. King's Quest V - CD version
8. King's Quest VI - CD version
9. Shannara (and 2 other Legend games - Death Gate CD Version and one more - all using the same engine)
10. Legend of Kyrandia 1, 2 CD versions
11. Dune (Adventure-Strategy Hybrid) - CD version
12. Mission Critical - 3 CD game which also supports GM standard
and others.
The Dig and Full Throttle have excellent speech quality for a DOS game, but they don't have support for MIDI.
If you want to count some others like :
Wing Commander II + Speech Accessory Pack - Full speech during flights, and during important cut scenes. The same goes to Ultima VIII CD version & Ultima VII with Speech Pack. Also Wing Commander Privateer with Speech Pack.
And some more games that I can't remember now...