Theres too many games that involve "Quantity" alone so I'm assuming you're referring to potency or having one's output volume considered superior?
There's a game here in early development that uses both as a mechanic:
Dryad Quest
Theres a function in
Breeders of the Nephelym where you harvest their cum. Different races have different value when sold.
Free Cities has a dairy where you can milk slaves. Over-productive prostates causes sperm to become diluted.
Theres a mini game in
Lilith's Throne where you compete with your potency with other bulls to win a prize.
My random JP recommendation goes to:
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(Audio Only) Your girlfriend get's knocked up right before your very eyes.