fallout 3, with over 300 hours total.
Now, I'll clarify a bit. i play on the PC and have the game overhauled with mods. in MY FO3, there are over 100 different guns, ranging from .32 semi-automatic pistols to 25MM HE Dismounted Flak Cannons.
I have all skills uncapped, over 100 added perks, and a lvl 100 lvllimit, I have new factions, rewards, and armors, I have a spawning mod which multiplies the number of enemies spawned by 3-5, and by 5 for feral ghouls, and i have a difficulty mod which removes additional hp when you level, drops base HP to a realistic amount(about 90), doubles all weapon damages, and makes injury effects much worse than vanilla.
My FO3 is a truly complete game, unlike the vanilla version.