In today's NHL with the way goalies have improved over the last decade(s) it is pretty much even in my eyes with actually a better chance that a goalie is the franchise player then a forward. This can also be represented by the fact that goaltenders have started to win the Hart and Conn Smythe (sp?) a lot more frequently in the last decade.
IMO it's harder for a player to actually become a franchise player then a goalie as there are just more players that are good/great, while there are a few that really stand out. I might judge a franchise player a little bit harder then some as I only consider great players like Lemieux, Gretzky, Yzerman, Iginla, etc. that are the backbone of their teams. While goalies like Roy, Brodeur, Hasek, Belfour etc. and then you have the goalies who have done really well for a few seasons that could also be considered as franchise players at the time Giguere, Kolzig, Theodore etc. come around more often in my opinion.