Unless you have something really heavy in mind, I would consider the typical, residential 40 PSF adequate (but with no live load reduction for large room size).
Forty PSF is a fairly substantial allowance compared to most "true" residential live loads. I describe it to people as equivalent to "wall-to-wall washing machines, all filled with water".
Concentrated loads, such as a slate pool table or grand piano may be another matter, but you most likely would have to deal with that at either 40 PSF or 60 PSF.
I agree that 40psf should be plenty for a game room. Most concerns come from bouncy/vibrating floors, and I think that stems from poorly or unblocked floor joists, or no ceiling applied in the area below.
If its a game room where they are playing board games, hanging out, watching movies, etc. then the 40 is fine. If its a game room where activities involving running, jumping, dancing, or broken bones, then the 40 is still fine, but I'd consider adding some mass to the floor to help dampen out vibrations.
![[reading]](/data/assets/smilies/reading.gif "[reading] [reading]")
