2.1+subpatches: Duty Roulette, Party Finder, Vote Kick, Abandon, iLvl display, FC Housing, Pharos Sirius, Haukke Manor (Hard), Copperbell Mines (Hard), Thornmarch, Labyrinth of the Ancients, The Minstrel’s Ballad:Ultima’s Bane, Ifrit, Garuda, and Titan Extreme, Sylphs and the Amalj'aa beast tribe quests, PvP: The Wolves' Den, Treasure Hunt

2.2+subpatches: The Second Coil of Bahamut, The Lost City of Amdapor, Halatali (Hard), Brayflox's Longstop (Hard), Whorleater Ex, Moogle Ex, Kobold and Sahagin beast tribe quests, Atma/Animus/Novus, Echo, Gardening, The Challenge Log, The Sightseeing Log, Soldiery, Master crafting, Big Fishing, Glamours, Retainer ventures, Materia Transmutation, gear preview, Titles, Cutscene Skipping

2.3+subpatches: Syrcus Tower, Savage, Hullbreaker Isle, The Tam-Tara Deepcroft (Hard), The Stone Vigil (Hard), Ramuh Ex, PvP: Frontline, Personal Housing, Private Chambers, Chocobo raising/coloring, Ixal beast tribe quests, The Hunt, Desynthesis, Skywatcher, Nexus

2.4+subpatches: The Final Coil of Bahamut, Snowcloak, Sastasha (Hard), Qarn (Hard), Shiva Ex, The Dragon's Neck, Ninja, Poetics, Eternal Bonding, Zodiac, Stoneskin II

2.5+subpatches: The World of Darkness, Gold Saucer, The Keeper of the Lake, The Wanderer’s Palace (Hard), Amdapor Keep (Hard), Urth’s Fount, Battle in the Big Keep, Crystalis, The Steps of Faith, PvP: Slaughter, Triple Triad, Choco racing/breeding, Zeta

3.0: Heavensward expansion and Alexander raid in subpatch.

3.1: The Diadem, Void Ark, Lord of Vermillion, Saint Mocianne's Arboretum, Pharos Sirius (Hard), The Minstrel's Ballad: Thordan's Reign, Vanu Vanu beast tribe quests, inactive housing demolition, Free Company name changing, adjustable lightning, a lot of minor QoL changes

I would say 2.1 was the best patch, despite having the worst scenario quests. Just imagine there were no such features like Party Finder or Roulettes before it.