Quoted from Daditude:I would really love to put a Godzilla side-by-side to an Ultraman.
Shhh. Don't share my secret plan.
Serious answer? Without playing either, I am expecting Godzilla to be a better game overall. That said if you were thinking about owning both I'd buy Halloween/Ultraman first. Why? Mostly because based on history, Stern is still going to be selling Godzilla in 2025. The spooky games won't be impossible to find, but they will be more inconvenient to find after collections have settled a bit.
In on Ultraman, FWIW.