Kirby has a lot of good hits all throughout the series. Kirby 64 was the first Kirby game I played, and it had a lot of great features that I wish were in other Kirby games, the most obvious feature being the combo ability system; while there were really only about seven kinds of powerups throughout the game, mixing them up created a ton of cool results, such as the snowball, light sabre, shuriken, fridge, etc etc. Kirby 64 also made creative use of its 3D sidescrolling system, such as the Shotzos in the snow factory level. One thing that I REALLY wish was in other Kirby games was the ability to hold enemies above you; granted, it wasn't always entirely useful, but it can actually be pretty fun messing with enemies like Bronto Burts throughout levels.
Kirby's Adventure was great for its time, and it's still great today; K:NMiD is a worthy remake, I personally think. I also really liked Amazing Mirror; it's mazish level design and boss mode gives it plenty of replay value, and it's also a welcome return of Kirby Super Star's ability moves system.
Kirby Squeak Squad was fun, but it does have issues; the bubbles were a nice idea, but horribly ruined the difficulty of the game. I also a have a beef with a couple of the bosses; the final boss is a lot weaker than you'd expect from a boss that appears right after you're given health item bubbles. Meanwhile, the imbalancedness of Mecha Cracko makes it so that you can choose the tornado ability, and you'll beat the boss quickly; choose fire, and you'll burn the platform you're standing on. And unless you're using the tornado ability, the boss is way too difficult, making it a poor choice for a third boss. Otherwise, I enjoyed messing around in levels from time to time.
Kirby's Air Ride...? I just used action replay, honestly. It's a little fun, but I'm not wasting my time completing tons of goals that I probably won't enjoy anyway just so I can unlock the cool stuff.
I'm currently trying to complete Kirby's Dream Course, and it's a lot of fun. I'm on Course 7 right now, and it's not easy compared to other Kirby games... XP