I started with Squeak Squad back before I even knew what Kirby was; it was one of my Christmas presents back in 2006 and 8 year old me was pretty interested in the game after seeing a commercial for it on TV. It was a pretty good introduction to the series for me, since me searching up info for the game led me to Kirbypedia (a now-defunct wiki site that has since been replaced by the Kirby Wikia), which taught me about all the other games and got me interested in the rest of the series.
In retrospect, Super Star and Ultra are both better introductions, since they offer a nice grab bag of different playstyles and presentations that can leave newcomers willing to explore the series based on what they did and didn’t enjoy. I honestly prefer the SNES original, since the new minigames & subgames in the DS version kinda felt too fillery to me (though Masked Dedede and Galacta Knight were some pretty welcome additions, since Masked Dedede had enough modifications to feel like a whole new opponent and Galacta Knight was, well, Galacta Knight), but that’s just my preference.