Opinions can change...
My new favorite episode is 'Cutie Remark.' I liked it when Starlight tried to get revenge on Twilight, the alternate universes are great. particularly liked the Crystal War segment, for obvious reasons. (the fighting)
Second is 'Cutie Map.' Starlight is a great character, liked the plot. Cutie markless is an interesting concept...
Third is 'Twilights Kingdom.'
Fourth is 'Rarity Investigates'
Fifth is 'Sonic Rainboom' which used to be my first favorite, but now...