For some of my characters...
Maple Harte: F.E.A.R. (The type of Combat, but with Stormtroopers instead of Replica Soldiers) + Kotor 2 (For Leveling) + Metro (Scarce Resources, leading to carefully thinking about upgrades, supernatural/psychological horror) + Bioshock (Multiple weapons and powers for use at any time)
Nine Lives: Think Vampire: The Masquerade, with Lightsabers (Story branching and leveling while managing your clan of space vampires, With her daughters as DLC) + Force Unleashed (Combat) + Thief The Dark Project (Stealth Segments
The Amalgam: The Darkness (Violent, Gory Combat and gunplay) + Dark Souls (Difficulty of Boss Enemies), + Legacy of Kain (Playing as an evil character engaging in dark sorcery)
Syd Celsius: God of War 2 (Combat and Bosses), + Dark Souls (Difficulty of bosses) Castlevania (Secrets and Upgrades)
Laertia Io: Dishonored (Combat), + Metro (Scarcity of Resources), + Far Cry 2 (With her seizures in the place of The Malaria)