I'll keep that in mind, a lot of those console ports are impressive technically but certainly aren't actually fun to play. I still have some PTSD with playing the NES version of King's Quest 4...
Here is the lowdown of the console ports of Ultima games:
3 NES: A decent port. I don't like it because of level scaling and the fact that Druids don't get fast MP regeneration they way they do in other versions, but the game is still quite playable, and even has a few extras (extra items to replace the times you need to enter specific words to do certain things, and an item that warps you back to town). Interestingly enough, in Japan this game got 2 MSX ports, and the one that was released on cartridge is a port of the NES version (the floppy version is more like other computer versions).
4 NES: A rather interesting one. It is very different from other versions, yet manages to be good in its own way. On one hand, I like the battle mechanics better (less RNG, and you can actually see how much damage you deal); on the other other, they did simplify NPC dialog and dungeons. One nice thing about this version is that it's a lot easier to play; you don't need to look up recipies (reagents are automatically used when casting spells like in Ultima 6), and you don't need to worry about mantras. One thing that's a bit odd: You can get into a fight while standing still. (Note that this game has JRPG-style random encounters.) It's worth playing this version, but it does not replace the PC version.
4 SMS: This version is more faithful to computer versions; it's actually my preferred version if I'm not playing NES. There are some nice improvements, like being able to attack diagonally (but not through walls, unlike NES), and being able to mix multiple copies of a spell like in Ultima 5, but the basic mechanics are still pretty much the same.
5 NES: As I said before, avoid this version; it's horrible. (Unlike the NES ports, this one preserves the original music instead of using entirely new tunes.)
6 SNES: Actually a reasonable version, but not as good as PC. Some simplifications were made, like the removal of many spells (mostly novelty spells, but there's no Enchant spell in this version), and the removal of the ability to attack arbitrary NPCs, but the graphics look identical to the PC version, and the music is improved (but still based on the same tunes, unlike the NES ports).
By the way, some other classic WRPG console ports are worth looking into; Wizardry ported pretty well (except that Wizardry 1 NES has a bug that makes AC not work for party members), Might and Magic 1 has a decent port (provided that you never let a Locust Plague enemy attack; a nasty bug turns this into a total party kill), and then there's the curious case of the Bard's Tale "ports", which are completely different games than their PC counterparts.