Probably gotta go with either Fallout 3 or The Elder Scrolls III: Morrowind.
I can’t choose between them and I don’t want to even look at the amount of hours i’ve put into either, i’ve lost months of my life to those games!
I think my favourite series might be the Devil May Cry games. Don’t even try to judge me, I have far too much unjust love for that series and I refuse to be ashamed :’)
And the most recent game that i’ve accidentally fallen in love with has gotta be 7 Days to Die. It’s unintentionally hilarious and fantastic in the way that only an already semi decent game still in beta can be, with the additional bonus that it’s actually a really solid game and it can’t lower in quality. They could release that build now i’d be happy with it!