I disagree with those who thought the anime should've ended in Johto, mainly because Ash didn't seem strong enough to win the League IMO. I think the show could've ended at the end of DP; Ash could've won the Sinnoh League had Tobias not been involved, though I don't think Ash would've been able to defeat Sinnoh's E4.
Hey, Ash and Pikachu took out a Dragonite owned by the Orange League Champion, I'm pretty sure they could reasonably pull off making at the very least Top 4 if not runner up or even winning the whole thing outright.
And for what it's worth, even his position in the Johto league was MUCH better than Hoenn. Yeah, sure, he got the same position as before in the latter, but that's exactly the problem, as he didn't actually GROW at all (at least with Johto, even if we ignore Orange Islands, he still increased in rank from the Indigo League, which did communicate some growth on that end. Hoenn just had him staying the same as before).
EDIT: And personally, I called the whole thing bullcrap regarding Tobias. It's as if the writers completely forgot that Ash's Pikachu had earlier single-handedly taken out Brandon's Regice with little effort (then again, they seemed to forget that tidbit starting with Gary beating Ash with Electivire, not to mention the two humiliating defeats Pikachu had to undergo against Paul, as well as Roarke, despite the fact that after beating Brandon's Regice, he really should have made mincemeat out of them. Maybe if Pikachu at least lost to Paul's Torterra, someone who actually IS close to Pikachu's experience level, I'd forgive it, but not when he lost against an Elekid and an explicit rookie Ursaring).