Ultima III

Ultima - I - II - IV - VI - VII - VIII - IX

The Ultima games are the most long-lived and successful in the CRPG genre largely because of the depth NPC and story interaction offers. You don't just ask characters you meet "Where's this?" or "Any rumors?"; You ask them about themselves, their lives, and the world around them. In the Ultima games, NPC's have virtual lives. They have personalities, concerns, goals, even schedules. - Justin A. Hussel in a Daggerfall review, now offline

Ultima III was the first Ultima game with music, in all versions except the one for the PC. It is therefore often recommend to play some other version rather.

The Exodus Project has released upgrades for Ultima II and III that fix some bugs, too. Graphics are converted to EGA, and III has midi music. There is also an upgrade for V that adds midi music.
Ultima III for Windows comes with EGA and VGA tilesets and can even be played at a screen resolution of 640×480.
Ultima III for the Macintosh is a remake by Leon McNeil. It features 32bit color but is gameplay-wise completely faithful to the original. It is shareware, registration costs $15, and requires system 7.5 or higher.

Ultima II and III exist in black & white Macintosh versions. These are the only Ultima game available in a Macintosh version.