I think the worst commonly used argument for ranking Patrick Roy over Dominik Hasek is the oft-invoked "4 Cups, 3 Conn Smythes vs. 1 Cup, 0 Conn Smythes". I've dealt with the issue of team success pretty much all along in this space so you've heard those arguments before, but I also don't like it when players are evaluated based on the number of Conn Smythes they win.
There isn't a more situational award in all of hockey than the Conn Smythe Trophy. I'm not trying to diminish the importance of playing great in the playoffs, I just don't believe that one's Conn Smythe haul is a good way to evaluate playoff success or to compare the relative performance of different players. The binary nature of the award (winner gets 1, all others get 0, only 1 award handed out every year) makes it more arbitrary. If you ranked all the playoff performances of the 1990s for every single player, for example, you might have three players from 1993 end up in the top 10 (Patrick Roy, Wayne Gretzky, Doug Gilmour). Obviously only one of them can win that year's MVP award, meaning that the others end up, by "Smythe only accounting", ranked below players from weaker postseasons that weren't at their level of play. Was Cam Ward in 2006 better than Dominik Hasek in 1999? John Vanbiesbrouck in 1996? Martin Brodeur in 2003? Olaf Kolzig in 1998? Ward's the only one of those guys with a Smythe, even though I wouldn't rate his playoff as even close to any of the others.
The rest of the team is obviously a big factor, since in almost all cases the Conn Smythe Trophy winner is from the Cup champion. To win the Stanley Cup, a player needs to have great teammates around them. There have been a number of absolutely terrific playoff performances by players whose teams ended up losing in the second round or the Conference Finals. Gilmour in 1993 and Peter Forsberg in 2002 are two of the most commonly cited examples, and we can also point to the more recent efforts of Alex Ovechkin and Jonas Hiller in the 2009 playoffs. As such, by simply counting Smythes you are at least partially giving double credit for team success. Being the best player on a Stanley Cup winner is a notable achievement, but that by no means signifies that player was the best player on any team.
A player's Conn Smythe chances depend a lot on who else happens to be playing great in that particular playoff season. In the 2009 playoffs, Sidney Crosby scored 15 goals and 31 points, which is more than anyone has recorded in either category since Joe Sakic in 1996. That sounds pretty deserving of some hardware, but unfortunately for Sid the Kid his teammate Evgeni Malkin scored 36 points in the same postseason, which means Malkin gets a Smythe while Crosby gets nothing. In other years there have been no singularly outstanding candidates and the writers more or less picked somebody out of a hat (2007 is a good example, the Ducks likely split the votes among a number of good candidates). If Crosby had the same playoffs as he did this year in 2006, 2007, or 2008 he would have easily won the Conn Smythe, probably even if his team lost the Final. Therefore, giving no credit to the second place guy makes little sense.
I also dislike the excessive focus on the Stanley Cup Finals in Smythe voting. Over a short series, luck has a big impact. A player can be driving puck possession and creating scoring chances and yet not have his shots or his linemates' shots hit the net for a few games in the Finals, throwing him out of Smythe contention. Again Crosby is a good example, as in the 2009 Finals he scored 1 goal on 16 shots while linemates Bill Guerin and Chris Kunitz combined for 0 goals on 32 shots. Sometimes the puck luck is against you, and that's pretty much the only conclusion you can make when a top line shoots 2% and hits more posts than they score goals over an entire series. Crosby's 3 points in 7 games cost him the Conn Smythe, but it looked to me like he was doing the same thing he had been doing all playoffs. The difference was that he was playing against tougher competition and the shots weren't going in.
The last thing is that, like any awards voting, sometimes the voters make debatable choices. I don't agree with the voters' choice of Cam Ward over Rod Brind'Amour or Chris Pronger in 2006, or Joe Nieuwendyk over Hasek in 1999, to give just a couple of examples.
If I was running the league, I would make the Conn Smythe voting results public so we could see who was finishing in 2nd and 3rd place. I would also adopt all-star voting for the Stanley Cup playoffs, like they do in international tournaments and at the end of the regular season. This would allow credit to be given to the players who were the best at their position but who may not have ended up with a ring because their teammates weren't as good.
Here is my attempt at putting together postseason All-Star teams for each season since the lockout:
G: Jonas Hiller
D: Nicklas Lidstrom, Brent Seabrook
F: Evgeni Malkin, Sidney Crosby, Alex Ovechkin
G: Marc-Andre Fleury
D: Nicklas Lidstrom, Sergei Gonchar
F: Henrik Zetterberg, Sidney Crosby, Johan Franzen
G: Roberto Luongo
D: Nicklas Lidstrom, Chris Pronger
F: Daniel Alfredsson, Sami Pahlsson, Dany Heatley
G: Dwayne Roloson
D: Chris Pronger, Scott Niedermayer
F: Eric Staal, Rod Brind'Amour, Patrik Elias
I doubt the Conn Smythe voters would have agreed with me on those teams (I left 2 of the 4 trophy winners off of my teams entirely). If you disagree with my selections, by all means take a shot at it in the comments. However, regardless of disagreements over a few individual cases, awarding All-Stars would give players like Crosby and Lidstrom the credit they deserve for their outstanding playoff performances.