Many improvements are overshadowed by new bugs
Wizardry on the NES was released after Dragon Quest/Warrior, which borrowed many ideas. Dragon Quest set expectations for console RPGs that Wizardry, as it was released on the Apple II, would not meet.
Many changes made to the NES version are improvements. Enemies are much more detail and the walls are solid (as opposed to a wireframe). There's even music, and it's actually a little catchy.
The battle system has been streamlined for the NES's controller. Menus are now selected using an arrow cursor and spells are listed (as opposed to having to type them out to cast them).
The NES version, however, introduced a number of bugs. The most significant is that AC,apparently, does nothing. This makes the game a lot more difficult, though that difficulty is offset by the easy of hitting the reset button on the console and abusing Wizardry's autosave feature.
The NES version also removed many puzzles that were present in computer versions. This was because they usually required text entry, though replacements for these would have been a welcome change to dungeon crawling.
One problem that Wizardry has in general is accessibility with its spells. To new users, the seemingly jibberish names for spells mean nothing. Without a manual, there is no way to know that dios heals wounds and malor can kill you instantly if you don't enter coordinates correctly. This sort of trial and error is very unfair, especially for the more dangerous spells like haman and malor that can has permanent consequences.
The Bottom Line
Wizardry is a simple game, with a simple goal--get to the bottom of the dungeon. The key to success isn't your ability to grind and gain levels--it's your ability and patience to map each floor in detail.
Mapping is something that may put off many users, but it is the key to what makes Wizardry the adventure that it is. The constant fear of getting lost, the dread of walking through a door and having it vanish behind you--the act of mapping is what connects the player to the adventure. As the party transverses the blackness of the dungeon, the constant unknown created by mapping engages the player in a unique dimension.
The is really what still makes Wizardry unique and worthwhile today. It isn't just one of the first RPGs, it's still an experience that many games that followed could not reproduce.