You explicitly said "metro area", which includes the suburbs.  Now you're excluding the suburbs.  You're moving the goalposts.  

And it's puzzling how you didn't understand the downtown/airport comment.  It was painfully obvious -- that's where most of the transit goes. Meaning the people that need to go there are the ones for whom transit can be a good fit for.  Meaning for the vast majority of the metro area that need to get SOMEWHERE ELSE, it's NOT a good fit for.

Rail transit to downtown Denver and DIA works (somewhat) because those are high density points. But if you expect most of Denver (let alone most of metro Denver) to become anywhere remotely close to that degree of population density, you're dreaming. And without that very high density, it's gonna be relegated to low usage. And it's way too costly to be justified for such low usage, and as a high-cost benefit for such a small% of the taxpayers paying for 70% of the cost.