Having never played a CD-i Zelda game I simply cannot say whether they are all as bad as common wisdom would have us believe, though, admittedly, common wisdom does seem to agree that Zelda's Adventure is indeed the worst of the lot. It's a digitized affair staring Zelda herself and one that is played from an overhead perspective where apparently everything went wrong. From the blurry digitized graphics and the horrid acting to the virtually non-existent music and the ludicrous difficulty, nothing really worked.
Still, the game is quite rare today and considered by many an important collectible for the CD-i, meaning that more than a few people should be interested in this Zelda's Adventure (CD-i) eBay auction. The game comes in its jewel case and the seller ships worldwide.