In my opinion, this is the best season, even with season 1 included. I love how season 2 does add more depth to Regina (not that she didn't in season 1), showing that the good guys like Emma and Snow aren't perfect, developing Belle's character, the couple of Emma and Neal, and Henry showing how much he loves Regina. Season 4 I'm really mixed about. The Frozen story ark SUCKED, since it was pretty much just a cheap cash grab of an awful movie that people won't let die. The only things I loved about it were showing the villain Ingrid and also the relationship between Regina and Robin. Unfortunately, they make a lot of bad references to Frozen and the characters from Frozen make A LOT of REALLY BAD jokes that are cringe worthy. Luckily Regina's wit was able to save the humor of this half of the season. However, the second half was AWESOME and really felt like Once Upon A Time, so much that it should've been the plot for all of season 4, since it's kind of rushed. Now for the reasons I LOVE season 3:

FREAKING ARIEL!!!!!!!!!!

Great character development (especially for Regina and Emma)

Regina finally become good

It has some of my favorite episodes EVER!

Zelena

Great writing

Peter Pan DIES (I've always hated the character of Peter Pan in general, even though this one is the worst, so it was SO THRILLING to see him die. Me seeing Pan die is how it would be for zanhar1 to see Bloom from Winx Club die.)

Emma and Regina building a relationship

Snow and Regina mending their relationship

REGINA AND ROBIN!

Regina's amazing sassy lines

Showing the character of Peter Pan as the true monster he is and not portraying him as a hero (Even Walt Disney himself hated the character of Peter Pan.)

Brilliant writing

AND MANY MORE!!!!!!!!!!!!!!!!!!!!!!

Then 2, then 4.

My order is 2, 3A, 4B, 3B, 4A.

Also season 4. I loved Ingrid, Anna, Elsa, Kristoff, QOD.

Even though S1 is and will always be the best <333 S3 is A W E S O M E <3

S1
S2
S3
S4

Even though it had its issues it was a good season overall.