From memory, Gauntlet II was just more of the same in regards to how it plays when compared to its predecessor. However, having now played both of the games in their original arcade versions, I can say that they aren’t exactly the same and that this one improves over the first one.
The level design in Gauntlet II is fantastic and a lot more maze-like than the original. Also, there is more visual flair in the designs with stunningly vibrant colors, as well as new kinds of walls and floor tiles. Playing this just after the first game really shows you how much this one has stepped forward in its overall look and style.
The game also seems to have more diverse groups of enemies to swarm you. Everything is almost the same regarding enemy types but they seem to be mixed up better. Instead of levels that are primarily ghosts, you now have ghosts, demons and trolls all coming at you from multiple spots in pretty close quarters.
If anything, this one was definitely a quarter thief.
I think the addition I liked most was the dragons. Every half dozen levels or so, you will encounter a pretty large, fire spitting dragon. They do massive damage but they also add a whole new level of coolness to the proceedings.
Gauntlet II is everything the original game was and then some. It’s a shit ton of fun and thankfully, I don’t have to dump actual quarters in it anymore.
Pairs well with: the original Gauntlet and then the later sequels.