It so totally depends on what criteria defines YOUR best burger.
Evelyn's on W. Broadway southside between Arbutus and and Yew (around the corner to Bex) is a Chinese/Canadian type place but they have an almost perfect "Diner burger." Unfortunately, the patty's standard beef, not thick, and cooked through, the char's hit'n'miss, BUT the bun has the perfect amount of butter and is toasted evenly and well on the grill, with just the enough mayo and "sauce" plus a very good "cheese." Shredded lettuce and a slice of good tomato on the bottom (season dependent, too - mid-summer burgers are better). Cheap at less than $7 with a soup. Both the bacon and the mushroom variety has an awesome salt-gradient; the patty is healthy and clean and delicious (and fatty and loose without being cloying) and the above-patty has a dose of saltiness to counteract the bottom. Lately, the bacon has been a lot more crunchy-dissolvey and generally awesomer.
Unlike a lot of "premium" burgers, everything fits inside the bun, and the bun doesn't dissolve. No messy fingers but no chunks of non-meat-ed bread.