Mountain Sun (from Boulder) just opened a pub in Denver
http://www.mountainsunpub.com/
on 17th and Vine near City Park.
If you are going to be in LoDo (ballpark area) you do need to stop off at Wynkoop for a hand pulled pint.
A block away from the Wynkoop is the Denver ChopHouse and Brewery. A good bet for a fine Pils and GREAT, if a bit expensive, food.
If the Rockies are out of town, stop by Blue Moon Brewing at the SandLot. The new name of the brewery at Coors Field. Tom and John, the brewers, are great guys and the brewing gear is pretty much state of the art for a 10 bbl system.
In Cherry Creek, the ONLY place to go is The BULL and BUSH.