Phantom Quest Corp is more or less average with little to offer, but is executed well enough to still be enjoyable. It's visuals are good, being well animated and colorful. It's looks are on par with most of the OVA's of the 90's that had decent budgets. Although it's looks are good, the character design is a bit bland. None of the designs particularly bad, but there's nothing to write home about either. Story wise it's sufficient. Being only four episodes it doesn't have much time to tell much of a story arc, and it's very episodic. Each episode tellsa simple story, that is enjoyable, but doesn't leave much impact. The series is a bit dependent on cliches. This doesn't detract a lot of the series, but don't expect anything new that will blow your mind.
The characters themselves are pretty stock and aren't developed much. This is forgivable considering that it only had four episodes to introduce them. Each character does have enough personality to make them interesting, but nothing good enough to stand out much. The best part of the series would be Rika Matsumoto's performance as the main character. She brings a lot of energy to the role, and makes it quite interesting. It's a shame that Pokemon is eating up all of her time, because it would be really nice to see her more often.
Overall Phantom Quest Corp doesn't have much to offer, but isn't something to avoid. It's not spectacular enough to seek out, but if you get the chance to give it a watch it's worth the time.