Don't get me wrong, I'm aware
L'Étoile Mystérieuse (The Shooting Star) is not as polished as subsequent albums. When I was a child I wanted to become an astronomer; I dreamed of ressembling those big-headed long-bearded balding scientists. I also dreamed of becoming a Montreal Canadiens player and an action movie star, like most kids, but astronomer was the deepest archetypal image I identified with. So in light of this it's not surprising that
L'Étoile Mystérieuse would rank as my favorite, as they were a ton of scientists in this album, as well as a connection to astronomy. What I liked about it was the symbolism, the themes, the spark to the imagination it triggered within me.
But even if I take the quality of the story as objectively as possible, putting aside all my personal childhood preferences (as much as is possible), I don't see how you could prefer
Tintin au Congo, Tintin en Amérique, Tintin chez les Picaros, or even
L'Oreille Cassée to this one.
Vol 714 pour Sydney was not that great neither.
Speaking of
Tintin au Congo, it was a completely insane album. Not only was it super racist, but the animal cruelty was nuts too. It was such an over-the-top contrast with the pure nature of the Tintin character as he is generally perceived in the popular imagination. I'm aware it was the first official album (unless you count Tintin chez les Soviets), and so Tintin's nature was not settled back then, but looking at it with hindsight makes quite an effect.
I leave you with some completely insane (and to be honest, hilarious) scenes from Tintin au Congo involving complete disregard for animal life: