I thought I had been to a fair number of stadiums, but I just went through the list and only 4 of the 11 I have been to are still in use. I'd rank those Coors, Ballpark at Arlington, Camden Yards, and then Fenway. I even liked old yankee Stadium better than Fenway, although I haven't seen it since they added the seats on top of the Green Monster.
Of the replaced stadiums, Yankee Stadium the only one on the list that was any kind of loss. Good ridddance to the Met, the Dome, Shea and Arlington. Busch and Riverfront weren't horrible, but they won't be missed either thanks to major upgrades.