Ultima 7's one of my favorite PC RPGs, but I'd recommend using the Exult engine to play it.
If you buy it from GOG it's bundled with DOSBOX, and it never really emulated all that well in Dosbox because it has weird memory managers. The original game also had some bugs and interface.
Exult addresses all of these issues and allows for a few useful mods (keyrings, which you definitely need, as well as, uh, something for sheep sheering).
The Worlds of Ultima games are freeware on GOG, as is Ultima 4. U4's a bit archaic, but I like it. You'll want to play it with XU4 or something though, as that re-adds the MIDI music.
Betrayal at Krondor (also on gog) is another great choice, although it's a considerably more challenging game -- the Ultima series from 4 onwards are much closer to adventure games with combat than traditional PC RPGs, and they've aged a lo better for it.
You can get the first six Might and Magic games in a bundle from gog.com too. The first two might be too archaic, but 4 and 5 are super-accessible. I like 6 a lot too though it's sort of gross looking.
Just to break stuff down, Krondor's focused on a really well-written narrative and fairly in-depth gameplay mechanics, the Ultima games are focused more on puzzle solving/exploration/world interaction, with 6 and 7 having a HUGE narrative focus, and M&M is mostly dungeon crawling, with less story.
Gothic 1 and 2 exist at a weird intersection of Ultima 7, Morrowind, Dark Souls, and Germany. Very solid, though.
Also I'm sure someone else mentioned this already but you can get the complete Avernum and Geneforce series off gog for like 20 bucks and have enough RPG to last you for a damn long time.
And for a non-PC recommendation? Summoner 2 on the GC/PS2. Really cool action RPG, big world, all the characters are really unique.
Daggerfall's freeware now if you want to check out what I personally consider to be the worst RPG ever made.