If you are ever in Vegas then go to the Burger Bar at Mandalay Bay.
Hands down the best burger I've ever had is their Hubert Keller Burger, which is a Buffalo burger that you can have medium rare and is the by far the juiciest burger I've ever had.
http://www.burger-bar.com/lv_menu.php
as for Calgary.....I really like Five Guys and Crafts new burgers are damn good as well.