Well, in truth, there were about 150 dogs, and twenty total mushers. You can see that information here (scroll down to my second post in the topic):
http://baltosource.timduru.org/board/viewtopic.php?t=8889.
Each of those dogs and their mushers, in their own way, were heroes. They each faced great dangers, including temperatures and conditions not ideal for dog sledding, in order to get the serum to Nome.
The reason Togo, Leonhard Seppala, Balto, and Gunnar Kaasen (the musher of Balto's team) stand out is because they each faced the worst parts of the route (in terms of terrain, weather conditions and temperature). And in the case of Seppala's team, they went nearly six times as far as any other team...and that Togo (who led Seppala's team) was leading the team at the advanced age of 12 years (which is old for a dog to be doing that kind of work). Togo deserved a lion's share of the attention...as did Seppala (who owned, bred and/or trained many of the dogs on the run).