Although Dragon Quest is one of the most popular game series in the East, it has never quite caught on in the West. Released under the banner of Square Enix, the series was often overshadowed by sister series Final Fantasy. While this never stopped any mainline entry from being released in the West (except for X, which is an MMO), I can't help but feel that Dragon Quest never got the due it deserved.
One thing I didn't mention is part of why it had such a big impact: It was a massive improvement in scope, gameplay, and storytelling over the two preceding Dragon Quest titles. With DQIII HD's sales success and its chronological position as the first part of a story trilogy, Square Enix releasing a similar HD-2D remake of the first two titles made perfect sense.