I recently played Advance Wars 2 with a few other friends using the single-pak mode, and despite its limitations (you only get the full game experience when everyone has the game) it was a blast playing a strategy game with fog of war with a few other friends on the gameboy.
I’ve heard good things about 4 swords, though personally it would be tempting for me to be a total asshole and interfere with my buddies attempts at finishing the dungeons. Which leads me to think of ideas: 1 team tries to get through the dungeon, the other team tries to stop them. However, I haven’t played the game yet, so it may turn out that you need all 4 people to get ANYWHERE. But having 4 links against bosses sounds fun 