One of my favourite NES games, and one of the latest ones at that, Kirby's Adventure is one of the most ambitious, colourful, and fully featured NES games to release on the entire system - where much like Super Mario Bros 3, it would act as the foundation for a lot of the series' tropes for years to come, although that can also unfortunately be to the game's detriment too. 

The first sequel to Kirby's Dream Land, Adventure is one of the last Nintendo releases for the NES, dropping in 1993, and as such, it's practically a technical love letter to the system, pushing pretty much everything to the limit in terms of sprite work, music, animation, and design. It says a lot to how quality this game is that you can still go back to this game and enjoy it mostly as much as any other game in the series.

To really get an idea for how much it set up for the entire series, this is the game where things such as Kirby's copy ability, a good chunk of the copy powers, and even story details like Kirby and DeDeDe's friendly rivalry, and even the series' regular plot twist of some kind of ancient evil being coming in to hijack the plot all originating here. The game's pretty damn lengthy with a full seven worlds to run through, each with six levels + a boss, along with a gigantic heap of various kinds of minigames that can be used to get different copy abilities and extra lives - something that you could consider the early form of the later extra games you would often find in later Kirby games.

The animation for this era is incredible, with each world introduced with a brand new animation of Kirby interacting with world in question, showing off what kind of new area you're about to explore. A lot of the game feels like it's the developers just showing off and flexing how much they can pull out of the NES' limited power. The locales are very varied, and helps to keep the game from feeling too repetitive, and there's even moments like the rotating tower where the game is just blatantly showing off just how well it is.

I wish I could really explain more, but really, a lot of it comes down to just how well they nailed the Kirby gameplay on something as limited as the NES, and how much it reflects upon the rest of the series and the skill of the development team to have so many aspects of the series figured out and decided, even with such an early point in the series. It's even where we get a fairly cinematic fight at the time with Meta Knight, where you battle in a sword dual and reveal he looks like Kirby under his mask. 

Even the story for this era is pretty neat, building off Dream Land's clash with DeDeDe in order to fake-out the audience when it's revealed in this game that DeDeDe isn't actually that bad of a guy, and he's actually taken the Dream Rod in order to save Dream Land from Nightmare's control. The animation helping this as the game conveys the story pretty well through it's short cutscenes and it's fun animations. It even has 100% completion requirements where the game tracks your completion and asks you to find all of the hidden switches to uncover all hidden portions of the worlds.

Unfortunately, Kirby's Adventure has one fatal flaw. It's a really, really bad flaw at that. The slowdown in the game is frequent and is downright unbearable. Pretty much at any point where there's more than two enemies on screen, or there's a fire-spewing enemy, the game slows down to a abject crawl, making it feel sluggish and horrible to play. With the game's ambition, and the excellent sprite and animation work, it means this slowdown happens super frequently. 

As a result, I also find it hard to particularly recommend Adventure. I know NES games is something where you expect slowdown, but this game's slowdown is downright extreme and happens very often at that. There was a option with the 3D version on 3DS, which did fix the slowdown, but it's unfortunately now impossible to get with the EShop gone. 

That is why I would personally recommend the GBA remake - Nightmare in Dreamland, which is pretty much a high-end remake of Adventure, with expanded story, abilities, minigames, and much more. It's how I personally enjoy playing through the game, and had it been present on the GBA Online service, it is easily how I would've opted to play it this time as well. Overall, Kirby's Adventure is both a technical marvel, but unfortunately a game held back by it's own ambition and pushing the NES just a bit too far than it could handle. But still, if you can play either 3D Classics Kirby's Adventure, or Nightmare in Dreamland, it's a easy recommendation from me.