There have been some damn good draft formats in the last three years, but there have also been a few duds. Based on the time-tested and clearly flawless method of trusting my own personal anecdotes, opinions, and gut feelings, I have undergone the extensive process of determining exactly how good each of these formats was in relation to its peers. Because they're not normal expansions, neither Modern Masters nor Conspiracy was included for consideration.
The official rankings are below. There is no appeals process.
1. Innistrad - Innistrad - Innistrad
2. Gatecrash - Gatecrash - Gatecrash
3. Magic 2013 - Magic 2013 - Magic 2013
4. Theros - Theros - Theros
5. Dragon's Maze - Gatecrash - Return to Ravnica
6. Journey into Nyx - Born of the Gods - Theros
7. Avacyn Restored - Avacyn Restored - Avacyn Restored
8. Magic 2014 - Magic 2014 - Magic 2014
9. Magic 2015 - Magic 2015 - Magic 2015
10. Dark Ascension - Innistrad - Innistrad
11. Born of the Gods - Theros - Theros
12. Fresh air and sunshine
13. Return to Ravnica - Return to Ravnica - Return to Ravnica (DIAF, Pack Rat)