What separates St. Louis from Heatley and many other seemingly more talented contemporaries is what exists on the inside. If you put Martin St. Louis' heart and desire into the body of a player as physically gifted as Heatley, there would be no discussion over the latter's HHOF candidacy. He would be a mortal lock. I have said this about Vincent Lecavalier as well. Put the heart of St. Louis into the body of Lecavalier, and you get a perennial Hart contender, not a guy who parlayed the only two elite seasons of his 13 year NHL career into an 11 year contract.
St. Louis is a ridiculously undersized forward that is extremely involved in the game when on the ice. He wears his heart on his sleeve and his ascent from too small to Hart winner endears himself to fans. That is why we look at him and generally hold him with far higher regard than we do someone like Heatley or even Lecavalier, forwards with insane physical tools that sometimes (especially in Lecavalier's case) play the game with the "I'm so talented that I don't need to go all out" mantra. St. Louis skates so hard; he plays with a chip on his shoulder even though he proved himself a long time ago. He makes the players around him better, evidenced by Vincent Lecavalier's two career seasons coming on his line and now Steven Stamkos reaching ridiculous heights.
As a Sharks fan, I can tell you that Dany Heatley is of no use to a professional hockey team unless he is scoring at least 40 goals. The first time I saw Heatley live as a Shark, I turned to my dad and told him I have never seen a player who stands around in the slot doing absolutely nothing yet somehow manages to score 40 goals consistently. Then, I saw Dany Heatley. He is no longer the explosive goal-scorer he was in Atlanta and Ottawa. Most of his goals are tap-ins at the front of the net and off rebounds, a far cry from the sniper that he was once. I like his previously unknown ability to go to the net, but he is far, far too reliant on a center getting him the puck to be the elite forward he once was. I like to joke that Heatley goes to the net and waits for Joe Thornton to shoot the puck off him into the goal. All that said, Heatley still possesses incredible talent, and he is simply having a bad year, likely the result of Joe Thornton's inexplicable point dropoff and sudden commitment to defensive play, maybe because of his captaincy. I'm sure he will be back to scoring around 40 goals next year. But his tendency to float around looking for a pass to magically find him is very annoying. You should have heard the Sharks' announcers three nights ago against Detroit when Heatley made a fantastic defensive play on the backcheck; it was palpable shock. I am pretty sure that this is the reason Heatley was removed from Joe Thornton's line. Thornton is still a work in progress defensively, but he's putting up Datsyukian takeaway numbers. Heatley is about as defensive as the Maginot Line. The flip-side, of course, is that he is generally useless without Joe to give him the puck.