Toronto doesn't make the playoffs because their fans will sell out the arena no matter what. Montreal is generally really tough.
In general the NHL is divided into haves and have nots, like most other sports. If you can afford to skirt the salary cap rules, have good management and coaching, you can put together a perenial team. That's about 8 teams in the NHL. Then there are another 16 teams on the bubble every year. who compete for the other 8 spots into the playoffs. Then there are the 6 teams that for a number of reasons just can't compete. The islanders, jets, panthers, jets/thrashers, bills, and lately the oilers fit this category.