demilich
AFAIK the Game Boy Color entries in the Wizardry Empire series are part of the same general "world", as in it's the same "Wizardry world" and the dragon god on the cover of the box of the games is very much Mr. L'kabreth, or Reiburesu in Japan; but the NPCs and the cities and the dungeons are all different ones and are most certainly simply in another "continent".
I use a lot "quotations" above because that information is simply speculation as none of that is completely spelled out for the player, but if L'kabreth is a dragon god in both the Game Boy Color games and in the PC/Playstation games then obviously the games take place in the same universe.
To put it bluntly however I would say that the Game Boy Color game of Wizardry Empire, which was Starfish's very first Wizardry game
ever, was simply a testing of sorts by Sir-Tech to see if they could do a traditional Wizardry game to Sir-Tech's satisfaction. It was Sir-Tech who wanted the japanese Wizardry games made, with the Empire series given the honor of 'canon', as they utilized L'kabreth for the cover of their very first game on the Game Boy Color, while the Gaiden series was pitched to Sir-Tech by success Studio as "Wizardry in Feudal Japan".
The Gaiden series' was given to success Studio (or suzak studio, depending on the game) based on the way they handled the japanese remakes of Wizardry 4 and 5 for Playstation 1 and Sega Saturn. Afterwards (I assume) they pitched the "Feudal Japan Wizardry" angle to Sir-Tech and they got the go-ahead.
So the Empire and the Gaiden series both came out at almost exactly the same time and they both began on the Game Boy.
BTW, demilich, if you want to play some good Wizardry Gaiden
right now then the English-language translation for Wizardry Gaiden 4: Throb Of The Demon's Heart for the SNES has just reached completion and there is a thread on this very forum.
Gaiden 1-3 were also translated, mostly by the same team who just finished Gaiden 4, and you can find them on Romhacking.net (as well as the English patch for Gaiden 4).
If you want to know what happened to the Gaiden series developers they went under and there a fifth Gaiden game developed called Wizardry: Dimguil, but it was the studios swan song. That game is only available in Japanese for the moment and it is for Playstation 1.
There is some awesome news though: about 8 years later success Studios came back under the moniker of Studio59 and developed for the PS2 the
amazingly good Wizardry Gaiden (6): The Prisoner Of The Battles. You can download an ISO of this game right now and play it on a PS2 emulator and have a great time as it features English-language options for the menus and items and enemies. It is not a story driven Wizardry game, unlike both Empire and Gaiden 1-5 which both series feature an emphasis on world-building and narrative (well, as far as those things exist in a Wizardry game).
Unlike the Empire games and Gaiden 1-5, Studio59's "The Prisoner Of The Battles" for PS2 is a completely hard-core remake of Wizardry 1-5 mechanics with the only additions being a weapons and armor Enchanting system. The focus of the games is purely on dungeon crawling, just like Wizardry 1-5, and there are no NPCs to talk to inside dungeons. That is not a complaint, btw, as I consider "The Prisoner Of The Battles" quite possibly the single most addictive and pure Wizardry game made outside of the original 5 scenarios. Its dungeons are
great and if you like dungeon crawling and building up your party and finding loot then you will love it.
There is a sequel to it, Wizardry Gaiden (still 6): The Five Ordeals, but although it also features English-language options they decided to implement a lot more puzzles into the dungeon crawling and since there aren't any guides available it would be quite hard or at least, difficult to enjoyably play through "The Five Ordeals" without knowing Japanese. This is in stark contrast to The Prisoner Of The Battles which I have finished without ever needing to look anything up even though I am not fluent in the language.
I highly recommend playing Gaiden 4 on the SNES, especially now that it was translated into English, and I also highly,
highly recommend downloading and playing Gaiden 6: The Prisoner Of The Battles which features English-language monsters, items, and menus and is a pure Wizardry dungeon crawl.
I am currently doing my best to translate into English Wizardry Empire 1 for PC and I have everything in English
except the NPC dialog and the dungeon Event Text; and those are required reading in order to play through the game effectively. Since I am not fluent in Japanese I am counting on the help of some of the same people who helped translate Gaiden 1-4 and Empire 2, and who are also currently working on Wizardry: Chronicle for Windows PC.
If you want to play what I have of Empire 1 in English the most current version is linked for download (the whole thing) in the Empire 1 thread right here in this forum. You can play through the 1st dungeon in English, but there are 3 dungeons in total and each dungeon features around 10 floors.
I have a menu translation done for Empire 3 on PSP but that one will never get the dialog/dungeon text translated because the files which contain the game script are compressed and I don't have the l33t hacker knowledge to decompress them. However if you wish to play Empire 3 for PSP with the items, monsters, spells and menus in English let me know and I can upload the most current version of my Empire 3 PSP English-ISO.