If you’ve never played a Phantasy Star game of the old line before, this is the best one, and the one you may as well start with if you’re otherwise too young to handle the first one’s relatively primitive (but still groundbreaking for its time) gameplay and story or the next two sequels’ flaws.

I strongly recommend playing Phantasy Star IV any way you can if you’re at all interested in an old-style JRPG with amazing production values and a setting that puts the sci-fi first before the fantasy, a novelty that is rarely matched even now.