Take a look at downtown Littleton. There are shops and restaurants, library, rec center, theater, but I don't think there is a good grocer you can walk to. Most important, there is a light rail station right there that will take you straight to downtown Denver. Getting to the mountains is fairly simple, as Littleton is south and a bit west of Denver. Drive straight west on Bowles to C470, you're in the foothills in 15 min, to Loveland in an hour.
I'm not sure about housing and rent ... it is mostly a mix of older, smaller houses and some new condo/townhouse type things. Most of the apartments nearby are older and not so nice, but there are older large houses that have been divided into apartments, too.
In Centennial there is a redevelopment called the Streets of Southglenn, which is a new area with shops and apartments, stuck in the middle of an older suburb. Light rail is not as close, but I'm sure you can bus or drive to it. There is a grocery store and a movie theater. Not nearly the same charm, as Littleton, which is a historic district with a main street.
Maybe Golden? I think they are building light rail down there now, but not sure where stations will be. Supposed to open in a couple of years. I can't speak to areas north of Denver. Most of the others south of Denver are basic sprawling suburbs. There are some newer areas between Boulder and Denver that I think were a little better planned than those south, but they don't have light rail yet, either. Not for 9 years, as planned.