for the record, seasons 2 & 3 were extremely hard to do because most, if not all, were such great episodes
Season 1
1. Siege of the north (parts 1 & 2)
2. The Waterbending Master
3. Bato of the Water Tribe
4. The Blue Spirit
5. The Deserter
6. The Fortuneteller
7. The Northern Air Temple
8. The Storm
9. Jet
10. The Waterbending Scroll
11. The King of Omashu
12. Winter Solstice: Avatar Roku
13. Winter Solstice pt. 1
14. The Southern Air Temple
15. Imprisoned
16. The Warriors of Kyoshi
17. The Avatar Returns
18. The Boy in the iceberg
19. that other avatar episode that doesn't deserve to be named on a list
Season 2
1. Crossroads of Destiny
2. The Guru
3. The Earth King
4. Lake laogai
5. The Drill
6. The Desert
7. The Serpents Pass
8. The Chase
9. The Swamp
10. Blind Bandit
11. Bitter Work
12. Return to Omashu
13. City of Walls of Secrets
14. The Library
15. The Avatar State
16. Tales of Ba Sing Se
17. Avatar Day
18. Appa's Lost Days
19. Zuko Alone
20. Cave of Two Lovers
Season 3
1. The Boiling Rock pt. 2
2. Day of Black Sun: the Eclipse
3. The Boiling Rock pt. 1
4. The Western Air Temple
5. The Firebending Masters
6. Day of Black Sun: the Invasion
7. The Puppetmaster
8. The Runaway
9. The Avatar and the Firelord
10. Sokka's Master
11. The Beach
12. The Awakening
13. The Headband
14. The Painted Lady
15. Nightmares and Daydreams