@RedSwirl Yes, anything before Ultima VI is going to be probably impenetrable to modern gamers.
Most critics will cite Ultima VII as the height of the series, from my view it is an excellent example of an early CRPG being ahead of its time in its attitude toward world manipulation and NPC’s having daily routines like in Skyrim. The difference is that this is 2D, old school clicking and questing. You could look at the general gameplay as being similar to a JRPG with a real time combat system, except you have an inventory and can pick up/craft objects if you want. There are also classic PC game dialogue options, which you choose to find out information you need to move forward. The story is not given to you freely, you have to question and explore.
Ultima VIII and IX were both considered dissapointments by critics and fans, but they are probably the most accessible of any Ultima games.
Ultima IX was very much ahead of its time in 3D open world RPG style, but it was practically unplayable at launch due too game breaking glitches and bugs, and some people could not get over the hilariously stiff dialogue. The game is still beautiful IMO, still very interesting, and does things that 3D RPG’s hadn’t begun to do till recently. The game is now perfectly playable with patches, and the GOG edition should play without problems.
Ultima Underworld I think holds up pretty well, its sequel I think even better. They are a lot like recent first person dungeon crawls like Grimrock and Undercroft, except true to old school fashion there are some points where you might get lost trying to figure out what to do. Easily remedied if your are using a FAQ. I think though that these are historically some of the best examples of the genre, though I think the modern versions are a little more accessible.