It is a good game.

There is one version that I can't recommend for serious play, and that would be the prototype English NES version. The problem with this version is that it is unfinished, and the game will crash if you go into certain areas, significantly limiting what you can do (and my understanding is that you can't even get close to the end of the game). With that said, if you can read Japanese, the Famicom version might be worth playing; there are some interesting additions, like the option to pay for healing and even resurrection (though it's not cheap from what I've read), and apparently the spells that are not obtainable in other versions are obtainable here.

With that said, I do not know if any actually released versions have bugs that would severely hamper one's enjoyment of the game, the way the bugs in the DOS and Amiga versions of Bard's Tale 3 do.

By the way, other early WRPG console ports that are buggy:
* Wizardry NES: AC does nothing for party members (so don't bother with armor)
* Might and Magic NES: If a Locust Plague gets even one chance to attack, it's game over.
* Might and Magic 3 SNES: One of the magic stats can't be boosted in this version. Also, this version plays rather slowly.

Early WRPG console ports that should be avoided entirely:
* Ultima 5 NES: A horrible "port" of a game, that tried to move it to an Ultima 6 style engine, but it worked rather poorly, and the game has many serious issues. In fact, this version turned me off to Ultima 5 so much that it was many years after getting the Ultima Collection (DOS versions of Ultima 1-8) for me to try another version.
* Might and Magic 2 SNES (Europe): This version was planned for US release, but didn't make it, probably because it couldn't pass Nintendo's QA. The game is horribly broken; for example, spells do 50 damage to enemies that save against them (even if the spell isn't normally that strong), instant death spells always work, enemy frenzy doesn't work (except for the enemy dying), and the game has been known to get stuck when trying to load. In other words, this game is broken. (Apparently there's a Japanese Super Famicom version that's different, but I don't know if it's any good.)

When it comes to early WRPGs, it can be very hard to find a good version, as it seems every version has its own unique bugs.

Just to be clear, you know GOG themselves don't do porting, correct?

I am describing early ports of PC WRPGs to consoles. Some of them worked pretty well (Ultima 4 got two nice ports, one reasonably faithful to the original and one which is very different but still good), while others, as I mentioned, were quite terrible.

Of all the ones I mentioned, the only one that you wouldn't be able to realistically acquire is the NES Dragon Wars prototype, as that version of the game was not released outside Japan, and the English prototype was clearly not in a releasable state. All the other console versions I mentioned actually did see release on cartridge, even though a few of them (Ultima 5 NES and Might & Magic 2 SNES) should not have been released in the state they were in.

The Sega Genesis port of Might & Magic 2 is certainly playable and not horrendously buggy, but I personally prefer the DOS version, particularly when you take into account the different bugs in both versions. I'd rather have the DOS version's bugs than the Genesis version's. (Anyone know how the other computer versions of MM2 compare from a bug standpoint?)

Edit: I an not aware of any modern re-releases of any of these early console WRPG ports.

A lot of this stuff is going to be relative with no "hard" definer of what a bad port is. Eg, Deus Ex 2 (Invisible War) is rated only 3.5 / 5 for a reason - it was a notoriously bad port / consolized released for PC where 80% of what made Deus Ex 1 had to be stripped out / scaled down to fit the original XBox's 64MB memory limit, and rather than design for PC then scale down to XBox, they designed for XBox almost 100% and just copy-pasted to PC. To me it still feels like a "bad port" (or at least 'severely missed opportunity' of a proper sequel to DX1).

Now 15 years ago I would have also included Thief 3 (Deadly Shadows) for suffering the same fate as Deus Ex 2 in being "designed for 64MB limited XBox" and being a pale shadow of the first two games for level size, minimalist UI, etc. However Thief games have such a great modding community that stuff like "Sneaky Upgrade" undoes a lot of the damage, adds proper HUD scaling (so "designed for 10ft view distance" no longer looks oversized or feels stupid when playing with a keyboard & mouse + monitor from 2-3ft away). IMHO it's still the weakest of the three, but it's also a lot more PC-friendly than it originally was. Same with Oblivion - stock UI is severely consolized vs Morrowind, but Darnified UI mod undoes most of the damage. Personally, I'd add DX2 to the list but not the other two - but someone else could very well argue that all three or none should be there.

What does "a really bad port" mean to you? If you don't specify, it'll be useless.
If the gameplay is the same without bugs than I don't care about nostalgia because I don't have such a memories for example about music. Without explanation about each game you could misguided someone.