Can I substitute mascarpone cheese with cream cheese?

Yes!

For more authentic flavor, combine with 8oz w/

2Tbs each whipping cream and sour cream.

probs

You could but its a softer texture than cream cheese, so it may not hold up as well.

Use Neufchâtel

I am told you can do this. I never have tried as when I find a recipe that sounds good using mascarpone, I wait to try it until I have all the ingredients called for. I keep cream cheese at all times as it is a very good snack portion.

Why on earth would you want to do that?

Sure. But it'll taste completely different.

Well it depends on what you are making.

Mascarpone will substitute for cream cheese in most respects (except, as Elendil mentioned, the precise taste), however it will not entirely bear the same structural qualities and may lead to your cookie spreading out a bit more than the cream cheese would have. <--- Google. I say go for it!