I just noticed that Celestia is a mix of all good traits of Mane Six, while she doesn't have any bad traits. She is also superior in every aspect. She's my favourite and beloved character and it is my biggest dream to be her, because I always wanted to be a kind and beautiful mare. So, why do I think that she's a mix of mane six?
Magic: She's the strongest and most powerful pony, probably only weaker than Sombra.
Loyalty: She's extremely loyal because she is loved by all ponies in the show. She keeps her promises and would fight to death for every pony.
Honesty: She never lied in the show, even once.
Laughter: Every time when Equestria is not in danger, she is very happy. She is also very laid back and slow to get angry. Also, she is obsessed with cakes, like Pinkie.
Generosity: Because nothing is more important to her than the happiness of ponies, she is very caring. We never saw any poor or homeless pony because she is so caring.
Kindness: She is even kinder than Fluttershy, very polite, and very gentle.
While this is a perfect recipe for a mary sue, I don't agree that Celestia is one. Remember that she is over 1000 years old, so she is emotionally developed and grown up. Also, it is implied that only the kindest ponies can be princesses.
So that's why she is my favourite character. I think that everyone here would love to hug her.