Congress Park

I have lived in one of the neighborhoods surrounding Congress Park area for most of the past several decades, and I can't recommend it highly enough. It's a great neighborhood with close access to the best of the city, and home and rental values that cover almost all income levels. Toward the southwestern end lies Congress Park itself. This is a small park by neighborhood standards, but it's extremely nice. There are open green spaces, sports fields and a swimming pool, surrounded by beautiful homes and treelined streets. But if that's just not enough park, Denver Botanic Gardens is right across the street, and Cheesman Park and City Park are both within a couple of minutes' drive! You won't be lacking for places to walk, jog, picnic, etc.
Much of the residential portion of Congress is made up of expensive brick bungalow homes. If you have the income to live on these blocks, you would be hard-pressed to find a better neighborhood. 7th Avenue Parkway in particular has a breathtaking strip of beautiful homes.
But if you can't quite afford those, there are many other options. North of 12th Avenue, many rentals make living much more affordable. 12th Avenue itself offers some wonderful little stores and restaurants which add to the charm and utility of this area. Along the Colorado Boulevard strip, there are both old and new apartment buildings with a broad variety of characters and amenities. The 13th and 14th Avenue strip also has many apartments for rent. This stretch of both Colfax on the north and Colorado Blvd on the east has some good little neighborhood shops, bars and restaurants.
Parking here is much more workable than in the neighborhoods just to the west, but this is still close enough to downtown to be very convenient. National Jewish Hospital lies on the southwest corner of Colfax and Colorado. This is one of the top respiratory hospitals in the world. People come from all over the country to seek treatment here. It's a cutting-edge research center, so the hospital offers employment opportunities right in the neighborhood. Overall, I doubt if anyone who moves to this neighborhood would ever regret it.