The Return of Ishtar

The direct sequel to the Tower of Druaga in the most literal sense - it starts exactly where that game ended, following Gilgamesh and Ki as they attempt to escape the tower.  Return of Ishtar is probably the very first co-op action RPG ever made, and I do mean co-op - having two players at the controls is required to play!  Thankfully, the game's action is considerably more straightforward than the puzzle-driven experience the first one provided, having Gilgamesh battle enemies in melee range (with touch combat similar to Hydlide or Ys) while Ishtar battles enemies at range with spells; however, if either player dies, it's a game over and you must spend a quarter to continue.  The layout of the dungeon is also considerably more complex; there are still 100 maps to go through, but now they're interweaved with multiple exits that can take you forward or back to previous rooms, so it's still a very long and involved process to complete.  Thankfully, you don't have to go through the whole thing in one long sitting - a password system keeps track of your progress through the dungeon.  It's also a fairly unbalanced asymmetrical experience - Gilgamesh's health drains when he attacks, making him completely dependent on Ki's healing to survive, while Ki gets all manner of ranged attack spells, supportive spells, buffers (including some that give Gil his only means to even harm certain types of enemies) and healing spells, and the camera only tracks her movement.  Basically, Player 2 just ends up being a glorified meatshield for Player 1, who dies in a single hit.  Worth a try for RPG historians as an interesting period piece that would lay the groundwork for co-op RPGs down the line, but there are many better such experiences to be had today.

Developer: Game Studio, Namco
Publisher: Namco
Released: 1986
Platforms: Arcade, FM-7, MSX, PC-8801, PC-9801, Sharp X68000, emulated versions are available on Namco Museum Volume 4 and as part of the Arcade Archives series on Switch.

The Tower of Druaga

An enormous hit in Japanese arcades but a pretty big flop in North America and elsewhere, Tower of Druaga is a rare example of an arcade dungeon crawler, putting heavy focus on battling enemies and discovering hidden secrets that upgrade your character's abilities to be better prepared for later challenges.  You really do need them, too - you start off atrociously slow on your feet, and your only way of killing enemies is by holding out your sword and running into them, done by holding the button down and waiting nearly a full second for your character to lower his shield and ready his sword.  Keeping it ready all the time isn't an option either, as you need your shield up to block enemy projectiles.  There are a surprising number of powerups to find - weapon and shield upgrades, boots that make you move faster, a pickaxe to knock down walls, items to show invisible enemies and light up dark floors, and even draw your sword more quickly.  However, they're all hidden behind secrets, usually with fairly obscure unlock conditions, making this a game that encouraged players to share knowledge with one another and cooperate to reach the end (but only after hours of trial and error and putting many, many coins into the machine, of course).  It also spawned a sequel and a prequel in the following years, making this one of the very first Japanese RPG franchises.  Even if you've never played any of those, though, you may have seen traces of it in some other Namco-published games like Tales of Destiny (as a similarly-designed 100 floor bonus dungeon), Mr. Driller: Drill Land, Soul Calibur III or Baten Kaitos.

Developer: Namco

Publisher: Namco

Released: 1984
Platform: Arcade, MSX, Famicom, FM-7, Game Boy, PC Engine, X1, GameCube, various Namco Museum compilations and digital platform releases.

Great Greed

There weren't a whole lot of localized RPGs on the original Game Boy, but Great Greed is one that manages to stand out from the pack and deliver a relatively fresh and unique experience.  Set in the "Greene Kingdom", a world with seven continents, the sense of humor is very apparent, with tons of character and location themed after food (Candy, Calorie, Lunch Box, Microwave, Sushi, etc) and silly enemies to match, including "Eye Cakes" and "Spud Buds".  Combat is surprisingly fast-paced, with both you and your opponents' actions occurring simultaneously and all actions being executed at the press of a single button - A is your normal attack, B is defend and the four directions on the D-pad are each mapped to one spell at a time (which must be equipped outside of battle).  It also had a fairly unique feature for its time in periodic Auto Saves, so if you venture into an area you can't handle and get whacked, you aren't totally SOL (which would make slightly more sense if saves were restricted, though you can also do so at any time via the Select button).  Further humor also comes from the choice at the end - after saving the world you can marry virtually any member of the royal family, even splitting up the king and queen to take one of their places.  As you can tell by the fact that you probably haven't heard of it, Great Greed wasn't a particularly strong seller and is pretty spendy these days; still, if you come across a copy, it's worth a look for its innovative elements and strange humor.

Developer: Namco
Publisher: Namco
Released: 1993
Platforms: Game Boy