Perhaps a look at the actual numbers of spells in each source might be useful?
These figures are based on the fantastic index over at
http://www.juicymango.co.uk/dndindex. I've included only those books published by WoTC, plus Dragon and Dungeon Magazine. There are, of course, plenty of duplicates between the sources, as many spells have been revised in later books, but I think the numbers are still interesting.
Players Handbook (3.5): 644 spells
Dragon Magazine (3.x): 332 spells
Magic of Faerûn (3.0): 237 spells
Complete Arcane (3.5): 165 spells
Complete Divine (3.5): 142 spells
Book of Vile Darkness (3.0): 141 spells
Oriental Adventures (3.0): 130 spells
Book of Exalted Deeds (3.5): 125 spells
Frostburn (3.5): 112 spells
Players Guide to Faerûn (3.5): 97 spells
Miniatures Handbook (3.5): 87 spells
Planar Handbook (3.5): 78 spells
Sandstorm (3.5): 72 spells
Complete Adventurer (3.5): 70 spells
Masters of the Wild (3.0): 67 spells
Tome and Blood (3.0): 65 spells
Draconomicon (3.5): 64 spells
Savage Species (3.0): 62 spells
Eberron Campaign Setting (3.5): 60 spells
Libris Mortis: The Book of Undead (3.5): 60 spells
Defenders of the Faith (3.0): 54 spells
Underdark (3.5): 52 spells
Epic Level Handbook (3.0): 48 spells
Forgotten Realms Campaign Setting (3.0): 40 spells
Races of Eberron (3.5): 38 spells
Shining South (3.5): 35 spells
Manual of the Planes (3.0): 31 spells
Races of Destiny (3.5): 28 spells
Dragonlance Campaign Setting (3.5): 26 spells
Lost Empires of Faerûn (3.5): 24 spells
Unapproachable East (3.5): 23 spells
Lords of Madness (3.5): 22 spells
Lords of Darkness (3.0): 17 spells
Races of Faerûn (3.5): 14 spells
Serpent Kingdoms (3.5): 14 spells
Deities and Demigods (3.0): 13 spells
Dungeon Magazine (3.x): 13 spells
Complete Warrior (3.5): 9 spells
Races of the Wild (3.5): 9 spells
Expanded Psionics Handbook (3.5): 8 spells
Races of Stone (3.5): 8 spells
Into the Dragon's Lair (3.0): 6 spells
Return To The Temple Of Elemental Evil (3.0): 5 spells
Lord of the Iron Fortress (3.0): 3 spells
Monsters of Faerûn (3.0): 3 spells
Sharn: City of Towers (3.5): 3 spells
Stronghold Builders Guide (3.0): 3 spells
Faiths and Pantheons (3.0): 2 spells
Shadows of the Last War (3.5): 1 spell
The Standing Stone (3.0): 1 spell