Sounds like you're looking for PC games that originated in Japan for Japanese PCs, though...right? Interesting topic. I'm guessing that the time period you probably care most about is probably pre-1985 or even pre-1983 (when the original Mario Bros. was released)
Found this article on the old NEC, but the thing is...
"It was a rare time when large numbers of Japanese gamers were actively interested in Western games, an interest which has only just rekindled in the last few years"
also:
"Yuji kept saying we should make an RPG, but while I wanted to make a game like Wizardry, he wanted it to be like Ultima. We said to ourselves that we'd combine the interesting parts from both, and what we ended up with was Dragon Quest."
http://www.hardcoregaming101.net/JPN...computers3.htm
So yes...Dragon Quest certainly does have a lot of well-known sequels, but given this quote, it's hard to argue that it was "ground-breaking." More like they continued to till the soil where Richard Garriott and the guys who made Wizardry while students @ Cornell had broken ground.
EDIT: I also think Warren Robinett's Adventure is probably a better pick as a precursor to The Legend of Zelda, as it contained a lot of the core elements: top-down cardinal movement, collection and use of items to overcome obstacles, and a fantasy theme.