Personally, I disliked F76. A friend of mine got it for me when it was on sale so we could play together - it's the engine/combat of FO4 (but with mandatory lag), and a solo building system like FO4's settlements (but without any NPCs).
GMod - now that brings me back! My nostalgia for it is so strong that I don't know I can give a serious opinion to The Young Folks(tm), but I burned literal hundreds of hours (admittedly at LAN parties) playing GMod and making stupid jokes with my social circle.
It's all fun and games until someone starts humanizing the watermelons...