Dragon Warrior was a modest success in North America (in no small part thanks to a Nintendo Power promotion giving away copies of the game for free), but a monstrous success in Japan, so naturally, a sequel was inevitable. Several sequels, actually, as the franchise continues to this day, spawning a number of spinoffs and side-games that all expand upon the original format in various ways. The core series has remained relatively constant in design, though, only getting modest updates and maintaining the same overall minimal design philosophy.
Still, it had to make significant leaps and bounds forward in some places, and Dragon Quest II may just be the series' most prominent example of that. This is evident right from the get-go, as the first thing you see upon starting is a fairly lengthy cutscene depicting the fall of the kingdom of Moonbrooke, with a single surviving soldier escaping to tell the king of Midenhall what happened. The player is then given control of the Prince of Midenhall and sets out on an adventure to defeat the evil Hargon.
A world-spanning one in this case, as the action in Dragon Warrior II is no longer confined to a single island, but a world map roughly four times the size of the original. The game is largely traversed on foot at first, but later in the game one unlocks the ability to teleport between specific points by unlocking teleporters across the planet, as well as sailing on the ocean via the ship (lending a nonlinear element to the proceedings). Dungeons are significantly longer too, as well as tougher, with quite a few more traps and puzzles to solve to make your way through. One also has the option to gamble in a few places too, which can earn the player some extra cash and prizes while giving them a short reprieve from constant battles for that purpose.
Going further, the game is no longer a quest undertaken by a single character. Instead there are now three playable characters, with the Prince of Midenhall primarily being a melee fighter with the ability to equip heavy armor and the strongest weapons, but unable to cast any spells. The Prince of Cannock joins later and is primarily a supportive character, being only an okay fighter but able to cast healing and supportive spells. Finally, the Princess of Moonbrooke is the weakest of the three physically, but can cast powerful spells that quickly wipe out enemies. This lends a bit more variety to the game than the original, as they also have quite a few more spells than were seen in the original game.
Naturally, enemies now appear in larger groups too - sometimes six or seven in a single battle, with enemies often taking on similar roles to those seen in the party. Bigger hard-hitting types are often seen with HP-restoring "Healers", and a line of strong enemies can be backed by a caster that deals heavy damage and is generally more of a threat than his protectors. The Wizardry influence is definitely felt here - both from the variety of enemies you face and just the general design of the UI, which consists mostly of windows and monster sprites on a solid black background. One slightly annoying element is that the player can only target specific groups of enemies and not individual units within that group, which can lead to you spreading out your attacks and enemies getting more turns in. Magic that targets entire groups does mitigate this to a small degree, but as in many JRPGs, you'll probably want to conserve the majority of it for bosses.
Like the original game, though, Dragon Quest II is a very grindy experience, requiring you to stop at several points and power up before you're tough enough to overcome a dungeon or a particularly irritating boss - a rather lengthy process as most enemies give very little in the way of experience. It can also get particularly frustrating in some areas, particularly toward the end where you hit a brick wall of difficulty, with areas packed to the brim by difficult enemies that can easily wipe your entire party. Which is only compounded in the penultimate dungeon, which is a lengthy maze of rooms that one must enter in a very specific way - one wrong turn sends you all the way back to the start to try again. But even worse than that is the final dungeon itself; while relatively straightforward, it is packed to the brim with encounters containing enemies that destroy themselves to instantly kill one of your characters, and if they happen to hit your healer, your run is pretty much ruined as you have no way to revive him (aside from a leaf of the Yggdrasil tree, which you are only allowed to have one of at a time). Basically, it doesn't matter how much you level up before coming here - getting to the boss relatively intact is just a matter of pure luck. Thankfully, most remakes of the game do at least throw you a bone here by giving the Princess a revive spell as well, so you can bounce back, even if at a considerable cost to your resources.
In short, Dragon Quest 2 is a logical extension of the first, adding a bit onto everything - a bigger world, more characters, more varied enemies and tactics, and quite a bit more challenge. It doesn't stray far from what made the original game popular, but that's part of the appeal for its fans, and for a game that dates all the way back to 1987, it was still quite novel to see a game with depth and longevity rivaling a PC RPG on a console. It may not be my favorite game of the era to revisit or even my favorite Dragon Quest game, but it's a fun piece of history and a decent RPG in its own right. Just be ready for it to become downright hateful as you approach the end.
Developer: Chunsoft
Publisher: Enix
Platform: NES, MSX, MSX2, SNES, Game Boy Color, Mobile, Wii, Android, iOS, 3DS, PS4, Switch
Released: 1987, 1988, 1990, 1993, 1999, 2005, 2006, 2011, 2014, 2017, 2019
Recommended Version: I'd recommend one of the remakes over the original release as they are reworked to be considerably less grindy and more balanced than the original release. The most easily-found one nowadays is probably the Switch or Android/iOS versions (though the Game Boy Color version is a personal favorite of mine).