Aren't most of these points really subjective? I mean, Belle being more likeable and admirable than Ariel? Ariel does not get the appreciation she deserves for outwitting a shark, saving a man from a shipwreck inferno and swimming him to shore and taking on Ursula in the climax. Ditto for the songs. I just enjoy the TLM and Aladdin albums more than BatB soundtrack. TLM soundtrack is still in my opinion, Alan Menken's greatest achievement.
As for the romance vs. epics part, technically Mermaid wasn't all that more epic in scope to BatB (though the underwater sequences were scintillating). Where both BatB and TLK fall short for me when compared to Aladdin and TLM are the cast ensemble. There is just a little bit of the chemistry and spark missing in TLK and especially BatB that the casts of Aladdin and Mermaid had.
TLK came when the Renaissance wave was at its commercial and critical peak with the build-up created by Mermaid, BatB and then Aladdin. It was destined to make more unless it sucked royally hard (like Pocahontas). It owes a big part of its success to those three movies. Also, there are critic lists (TimeOut being one that I remember), where Aladdin is the highest ranked Renaissance movie.
That's Disney reasoning. TLK was the highest grosser and BatB got the BP nom so they tend to believe those two movies are the stronger of the Big Four, whether it is actually true or not. Also, in the 90's, it was Mermaid and Aladdin that received highly successful television spin-off series. In fact, Aladdin merchandising was EVERYWHERE in the 90's. We've discussed this in the Frozen thread last year, but post-9/11, Disney has definitely de-emphasized Aladdin. That plays into it being shoved into the Vault for some time as well.
You can make a highly appealing, troubled adult character. Matthew Broderick's Adult Simba wasn't that. At all.