That's still 18 novels in three years. Or, rather, a heck of a lot more novels than supplements.
Again, you might be surprised. It depends if you count the large number of Living Forgotten Realms adventures released for public play during this time. But even if you don't, the number of novels published over the last few years is definitely not "a heck of a lot more" than the number of published supplements which take place in the Realms.
2012: 12 novels + ebooks, 8 supplements, 35 LFR adventures
2013: 5 novels, 6 supplements, 19 LFR adventures
2014: 3 novels, 5 supplements, 16 LFR adventures
2012
EPIC 4-1: Shooting the Moon
NETH 4-1: Containing Shadow
TYMA 2-4: Stand Against the Darkness
AGLA 2-3: Sojourner's Way
NETH 4-2: The Tripartite Tower
NETH 4-3: Purifying the Prophet
SPEC 4-1: Cerulean Dreams
Halls of Undermountain
SPEC 4-2: The Writhing Obelisk
WATE 3-1: Moon Rising
Web of the Spider Queen
CALI 3-4: Fragments of a Shattered Mind
Spiderkiller
CALI 4-1: Plain of Stone Spiders
CALI 4-2: Dragon Above, Desert Below
CALI 4-3: Twisted Rune
SPEC 4-3: Conflict in Calimport
SPEC 4-4: Mischief in Memnon
Menzoberranzan: City of Intrigue
Council of Spiders
CORE 4-1: Eastern Carnivals
CORE 4-2: Legacy
MYRE 4-1: My Realms: Calimshan
SPEC 4-5: Rising Darkness
WATE 4-1: Paying the Piper
WATE 4-2: Rivals
WATE 4-3: The Devil's Denouement
Kill the Wizard
EPIC 4-2: Age of Ruin
Ed Greenwood Presents Elminster's Forgotten Realms
War of Everlasting Darkness
ABER 4-1: The Price of Freedom
ABER 4-2: A Dream Frozen in Amber
ABER 4-3: A Little Rebellion
CORE 4-3: Running Amok
CORE 4-4: Shadow Siege
ELTU 4-1: Born by Fiends
ELTU 4-2: The Iriaebor Gambit
INTR 4-1: Born Every Minute
SPEC 4-6: Raging Shadows
INTR 4-2: This Way to the Egress
CORE 4-5: Skeletons in the Closet
EPIC 4-3: Dark Hearts of Madness
2013
CORE 5-1: Churning Shadows
CORE 5-2: A Radiance Faded
ELTU 4-3: Minutes to Midnight
ELTU 4-4: The Fall of Elturgard
SPEC 5-1: Morthac's Mansion
SPEC 5-2: Closer to the Heart
QUES 4-1: Liberation
Storm over Neverwinter
Vault of the Dracolich
Search for the Diamond Staff
CORE 5-7: Broken Light
CORE 5-8: The Dantalien Maneuver
CORE 5-9: Last Testament
EPIC 5-2: Dragons Dark
SPEC 5-3: What Distant Skies
SPEC 5-4: Sky's Favor
Ghosts of Dragonspear Castle
Murder in Baldur's Gate
PREQ 5-1: Edge of Justice
NEVE 5-1: Hound's Baying
NEVE 5-2: Serpent's Kiss
NEVE 5-3: Spider's Web
WATE 3-2: Deepest Shadow
WATE 3-3: Dark Ranger
Legacy of the Crystal Shard
2014
CORE 6-1: Behind Obould's Lines
EPIC 5-3: Shadow Storm
EPIC 6-1: Confrontation in Shadow
SPEC 6-1: Divide and Conquer
Scourge of the Sword Coast
MYTH 6-1: Preemptive Strike
MYTH 6-2: Ambassador, General, Herald, Spy
MYTH 6-3: The World Will End in Fire
Dead in Thay
ADCP 1-1: Jungle Hunt
ADCP 2-1: The Paladin's Plague
ADCP 2-2: Heart of the Desert
ADCP 3-1: Swarm of Chaos
ADCP 3-2: From Dawn Till Dusk
ADCP 4-1: City of Destinies
ADCP 4-2: The Lost City of Suldolphor
ADCP 5-1: Home's Last Light
ADCP 5-2: The Best Defense
D&D Starter Set
Hoard of the Dragon Queen
The Rise of Tiamat