The only ones whom are are not my favourite in the film
Cinderella: The mice
Jasmine: The Genie
Mulan: Mushu

Hmm. Movies where the princess is not my favorite character. Gee. Let's see. I actually think it's about half of them.

From Aladdin: Genie is my favorite character. I love him.
From Brave: Elinor and Fergus are the ones who steal Merida's spotlight completely. In reality, they make the movie work.
From The Princess and The Frog: Charlotte La Bouff is so over the top and laugh-out-loud funny, she makes Tiana look so staid and priggish in comparison. I like Lottie a lot.
From Beauty and the Beast: I'll admit that Cogsworth does have that modicum of stuffy pride, but even he doesn't exude snobbery towards Lumiere and other people. To a word, Cogsworth isn't vain. Belle is vain, though.
From Sleeping Beauty: No offense. Merryweather soundly steals the show from the prince, the princess, and her fellow fairies. She also makes Maleficent look like a rotten egg. Yeah. Go, Merryweather!!!

In all the others, I think the princess seems to take the cake from even the stellar sidekicks. And that's a serious accomplishment...because most of Disney's sidekicks are such tough acts to top. And I gravitate toward sidekicks...

There are only a couple movies where I like other characters more than the princess:
Sleeping Beauty - I love Merryweather
Tangled - Mother Gothel and Eugene both completely steal the show here. I would much rather watch a film about either of them than about Rapunzel. They are both much more complex, interesting characters. I would LOVE to know Gothel's backstory!

at the end, Ariel becomes princess and Ariel is my fav princess, so some of the time

Only a few Disney Princess movies that have characters that I like better than the princess:
Sleeping Beauty - the three good fairies, they are completely steal the protagonist role from Aurora.
Aladdin - Aladdin and the Genie definitely. They both have better characteristic than Jasmine.
The Princess and the Frog - Charlotte, I like her spunky and her personality a lot, much better than Tiana.

mostly but here are the exceptions:
Sleeping Beauty - 3 fairies are the total protagonists here
Aladdin - Aladdin and Genie steal the limelight
Brave - Elinor plays an equally important role, without her, Merida is incomplete.

I only truly like as princesses Poca, Meri and Rory, so yeah, it's often the sidekicks or the villain that holds my attention (I only really dislike one princess though, I'm neutral on all the others. but in Aladdin for example Genie and Jafar are much more engaging than Aladdin or Jasmine. In Mulan I only like the three stooges soldiers, or in Cinderella that despite rooting for her, I much prefer seeing the scenes at the palace over the mice. or in Tangled that I don't care for anyone therefore I don't care for the movie