Season 1-Well it started it all. While I'm not a big fan, but still not a terrible episode, of this it did bring the first Rarijack (Look Before You Sleep). It still gave me my favorite shipping. Sonic Rainboom was my favorite episode of this season.
Season 2-It improve on season 1 and made me start to like Rarity better. Also the season I truly joined the fan base. A Friend in Deed was my favorite episode. Smile, Smile. Smile !
Season 3-An underrated season IMHO. It brought back the return of Trixie and Discord. It just tamed my hatred for RD with Sleepless in Ponyville and Wonderbolts Academy. Also Apple Family Reunion brought us like the first Applejack solo (IIRC) song being "Raise This Barn". Also this line, nuff said (Though Attend to forget the actual line ). It improve Applejack's role a main character after how fans kind of treated her in season 2. Magical Mystery Cure somehow is my favorite over Apple Family Reunion.
Season 4-Simple Ways, Rarity Takes Manehattan, The Breezies, Maud Pie. Oh continue the momentum of Applejack. The finale was pretty solid, too!
Season 5-Oh boy, this is a season I quit the show, but that don't mean it didn't have its moments. Like actually getting to see Moondancer, Gilda and RD becoming friends again. Slice of Life and Do Princesses Dream of Magical Sheep.