Okay. You know what? Best is subjective. Such an amazingly subjective term.
...in saying that, I know that it will do nothing to stop the comments section. Let's roll on regardless with a look at some of the best cosplays of 2015, according to me, some shmuck with an opinion and a platform upon which to air it. Most of these are here because they're impressive or worth bare minimum an amused chuckle, while the very best provoked both.
If you happen to see yourself or somebody you know featured here without credit, please let me know in the comments! A genuine attempt was made to gather as much information for crediting as possible, but cosplayers are occasionally quite mysterious folk.