You can argue about tropes all you like, but in fairness, it was a human fleet that took down Sovereign and a human leading a mixed race crew that hounded Saren at every turn.
Nonsense. Shepard wasn't the only person leading a force of aliens to fight against Saren. What about Captain Kirrahe? He lead the assault on Saren's base of operations on Virmire and WON. If it wasn't for Kirrahe and his leadership skills, Saren would still have his base of operations on Virmire.
And you can't really discount the Asari and Turian fleets that played a part in the Citadel battle either. The human fleet didn't have a "special" ability that the other species lacked that caused them to win the battle. All they did was just bring in a good number of ships and destroy sovereign. The Turians and the Quarians have a much bigger fleet than the humans.
And Shepard isn't a hero because she is human. She's just a human who just happened to be the hero. Any member of any race could have made contact with the Prothean Beacon and work towards the same conclusions that Shepard made. We know for a fact that the Beacon also works on Turians and Asari and both are very capable and intelligent races. Heck, it took an Asari just to make heads or tails on what the darn Beacon actually meant.