Since I'm greatly enjoying this game: are there comparable games?
The Journeman titles look quite similar; would part 3 be recommendable? Thank you!

Well, noticing your outcry, I thought you could get help by someone who knew "Journeman" which sadly I don't.

However, a serious question within the zork genre deserves at least half an answer so here goes.
I don't know of a graphical version of any adventure game that are close to zork GI, humor and all (they got it right with the Gran Inquisitor game, not that Zork Nemesis is bad, it's just a tad different so you may try that and see if you like it).

The last game I heard of which seeks to go the Zork/Infocom route was "Hadean Lands", but that is a true IF game, meaning it is text only. It received a few prizes in the IF genre, but it may not mean anything... I have just bought it and have not found time for playing it myself.

I would recommend Return to Zork. It is pretty good and funny and think you may like if you liked Zork Grand Inquisitor. Zork Nemesis is a very good game too, but not on the funny side. It's more esoterical and grim.
As far as the Journeyman games, I think they are more like the Myst games than Zork.
Maybe a Tex Murphy game?

Now, I forgot all about this thread and somehow stumbled upon it today.

To RenKalan first; If there's a question about Zork - Grand Inquisitor (which must be considered an introduction to the adventure genre and to the Zork universe), I would imagine RTZ to be a hars way to send him?

However, since you are on the trail of the Zork universe, please allow me to complete it:
Text adventure games (Interactive Fiction):
Zork I (1980)
Zork II (1981)
Zork III (1982)
Beyond Zork (1987)
Zork Zero (1988) {New graphical interface}
Zork - The Undiscovered Underground (1997) (Prequel to Grand Inquisitor)

Graphics adventure games:
Return to Zork (1993) {CD version with more graphics than the Floppy disk ed.}
Zork Nemesis (1996)
Zork Grand Inquisitor (1997)

Now, that was Zork... The Infocom universe stretch a little further though and as such...Here is a chronologic overview of all 43 Infocom releases for PC from 1980-1989. After 1989, the Infocom name was only used as a label and so they were left out...There's even a NES console only release named 'Tombs and Treasure' from 1988 (a lackluster adventure/RPG game set in the ancient ruins of Central America and not much to write home about).

1980 - Zork I
1981 - Zork II
1981 - Deadline
1982 - Zork III
1982 - Starcross
1983 - Suspended
1983 - The Witness
1983 - Planetfall
1983 - Enchanter
1983 - Infidel
1984 - Sorcerer
1984 - Seastalker
1984 - Cutthroats
1984 - Hitchhiker's Guide to the Galaxy
1984 - Suspect
1985 - Cornerstone
1985 - Wishbringer
1985 - A Mind Forever Voyaging
1985 - Spellbreaker
1986 - Ballyhoo
1986 - Fooblitzky
1986 - Trinity
1986 - Leather Goddesses of Phobos
1986 - Moonmist
1987 - Hollywood Hijinx
1987 - Bureaucracy
1987 - Stationfall
1987 - The Lurking Horror
1987 - Nord & Bert
1987 - Plundered Hearts
1987 - Beyond Zork
1987 - Border Zone
1988 - Sherlock: Riddle of the Crown Jewel
1988 - Lane Mastodon vs. the Blubbermen (Visual novel)
1988 - Gamma Force: in Pit of a Thousand Screams (Visual novel)
1988 - ZorkQuest I: Assault on Egreth Castle (Visual novel)
1988 - ZorkQuest II: The Crystal of Doom (Visual novel)
1988 - Quarterstaff
1988 - Zork Zero
1988 - BattleTech
1989 - Shogun
1989 - Journey
1989 - Arthur

That's pretty much the whole story of Infocom, not even excluding their database application 'Cornerstone' from 1985...by many considered what would be their downfall.

On another note: The original Zork was ported over from mainframes in the late 1970s. It is one of the first text adventures and is widely considered to be one of the great classics of the genre which reached the peak of its popularity in the 1980's. Not that I ever really moved on from enjoying great text adventures (IF if you will) ;)