I don't even think Pikachu would.
Pikachu is powerful but in a different way. Pikachu is an underdog that fights from below. His strength is "inside", it isn't as open and obvious as Charizard. Pikachu would be celebrated, but not given the outright worship that Charizard got in that episode. Charizard is, openly and obviously, a warrior. A king. They make that very clear. Pikachu's greatest victories are insane miracles of an underdog overcoming the odds. Charizard's greatest victories are hard-fought battles between two warriors.
Besides, I think Pikachu's power fluctuates too often. Pikachu, at his absolute PEAK, is maybe slightly stronger than Charizard, but even that is hardly set in stone. But Charizard offers a level of consistent strength that no other Pokemon in the series matches.
Like, the writers would NEVER have Charizard lose to Panpour, like Pikachu did earlier in this series. They would never have Charizard tie with an Elekid after beating Regice. Charizard's key losses are only highlighted because of how rare they are. Blaziken is one, which I would say is Zard's only absolutely legit loss since he became the all-powerful beast we know today. Dusclops is another, but that was very cleverly written; it was made clear that it was completely Ash's fault. Besides, Charizard has two - two! - high profile losses. I mean, should I even list Pikachu's?
I think bringing up Zard being frozen by Poliwrath is a bit unfair - clearly that Charizard was not the strongest. But Charizard has trained and grown a lot since then. That younger, more inexperienced Charizard, hypothetically, couldn't beat Gary's Blastoise and Golem.
Now, I can see what you're thinking. Charizard is allowed a weak performance against Poliwrath but Pikachu isn't allowed one against Elekid (etc)? Well, the difference is the unreliable, constantly fluctuating nature of Pikachu's power. Pikachu has been written in such a way that he can lose or win basically any match and people won't be surprised, barring some extreme circumstances. Like, everyone was irritated when Pikachu lost to Cress, but I don't think they were particularly surprised. It's standard Pikachu fare at this point. But the writers would never, ever, have Charizard lose in that situation. As I said, the Charizard that was frozen by Poliwrath is not the same one that just had an episode dedicated to how amazing he is.
And that's the difference, I think. Charizard is Ash's trump card, his strength is protected by the writers. Pikachu is in a position where it pulls off amazing, miracle wins, but also takes some heavy losses. I don't think I can in good conscience say that Pikachu is the stronger Pokemon.