I nominate Slam Dunk. Sincerely speaking, I haven't read many sports mangas, but that's not going to make me abstain on this topic. First of all, as a fan of Takehiko Inoue it would be a shame to not nominate Slam Dunk or Real. Second, it's not only about being Takehiko's fan, but as a sport's fan as well, I respect and admire the realistic approach Inoue done in Real, and in less scale in Slam Dunk. Third, both mangas are artistically fantastic (Hey, it's the same guy that draws Vagabond). Fourth, very good stories. You might be asking (or not) - Why Slam Dunk instead of Real? - The answer is very simple, I equally like both, it's not about the Shounen vs Seinen thing, I just tossed a coin and Slam Dunk was the lucky one.