I'm going to explain why he's my favorite and defend him all at once although in truth he should need no defense but I see a lot of you nikkas is still sleeping.
As a kid, he became my favorite because blue is my favorite color and he had two swords. What kid doesn't like swords? Now as a teen and an adult, he stayed my favorite because we have a similar personality. He's a born leader, he's the most sensible of the turtles, he's the illest when it comes to giving all three of them work if need be, and he's the one who's going to handle business no matter the cost. The idea that because he doesn't get out of line or get all in his emotions and feelings like Ralph doesn't mean he's boring or doesn't have those emotions. He's the most mature of the bunch, so by nature he's going to be a combination of all three but know how to balance out the same traits they have along with his own inquisitive nature, his own determination and wisdom. The 03 cartoon, the 07 animated movie and the comics flesh his character out the most because in a lot of ways, he's like Clark Kent or Peter Parker: The guy who always wants to do the right thing and normally will but that doesn't mean there is no conflict or that it's always easy for him. There's a burden that comes with leadership and a burden that comes with always being expected to succeed and exceed expectations and he encompasses all of that. As Splinter told him once, "There are no excuses when you are the leader my student"