Playable summons of every mainline game:

FF3

Chocobo
Shiva
Ramuh
Ifrit
Titan
Odin
Leviathan
Bahamut

FF4

Asura
Bahamut
Bomb
Chocobo
Cockatrice
Goblin (Imp)
Ifrit
Leviathan
Mindflayer
Dragon (Mist)
Odin
Ramuh
Shiva
Sylph
Titan
Whyt

FF5

Chocobo
Remora
Sylph
Ifrit
Ramuh
Shiva
Catoblepas
Golem
Titan
Carbuncle
Odin
Syldra
Bahamut
Leviathan
Phoenix
Eggman

FF6

Alexander
Bahamut
Bismarck
Cait Sith
Carbuncle
Catoblepas
Crusader
Fenrir
Golem
Ifrit
Kirin
Lakshmi
Maduin
Midgardsormr
Odin
Phantom
Phoenix
Quetzalli
Ragnarok
Raiden
Ramuh
Seraph
Siren
Shiva
Unicorn
Valigarmanda
Zona Seeker
Cactuar
Diabolos
Gilgamesh
Leviathan

FF7

Alexander
Bahamut
Neo Bahamut
Bahamut ZERO
Choco/Mog
Hades
Ifrit
Leviathan
Knights of the Round
Kujata
Odin
Phoenix
Ramuh
Shiva
Titan
Typhon

FF8

Alexander
Bahamut
Brothers
Cactuar
Carbuncle
Cerberus
Diablos
Doomtrain
Eden
Ifrit
Leviathan
Quezacotl
Shiva
Siren
Pandemona
Tonberry
Angelo (arguably)
Odin
Gilgamesh
Phoenix
Boko
Mini Mog
Moomba

FF9

Dagger\\'s summons
Ramuh
Ifrit
Shiva
Atomos
Odin
Leviathan
Bahamut
Ark

Eiko\\'s summons
Fenrir and Titan
Phoenix
Carbuncle
Madeen

FF10

Valefor
Ifrit
Ixion
Shiva
Bahamut
Anima
Yojimbo
The Magus Sisters

FF11


Carbuncle
Fenrir
Diabolos
Ifrit
Titan
Leviathan
Garuda
Shiva
Ramuh
Alexander
Odin
Atomos
Cait Sith
Siren

FF12

Belias
Mateus
Adrammelech
Zalera
Shemhazai
Hashmal
Cúchulainn
Zeromus
Exodus
Famfrit
Chaos
Ultima
Zodiark

FF13

Odin
Shiva
Hecatoncheir
Brynhildr
Alexander
Bahamut

Now, in contrast, in FF14, we have:

Carbuncle
Ifrit
Titan
Garuda
Bahamut
Phoenix
Solar Bahamut