Sam and Dean are the best because despite all the doom and gloom they go through they can still find ways to enjoy themselves. They'll never give up on each other and they will continue hunting monsters until the world is ready to say goodbye to Sam and Dean Winchester. Let's hope it's not too soon!
Dean first love is baby but he still took time to show Sam how to take care of her. Of course he was showing him how to fix her because he was going to be dying but you still have to appreciate Dean letting Sam have some control.
A lot of people would cal Dean refusing to close the door to hell as selfish but Dean has never minced words when it comes to his brother. It's always just been Sam and Dean against the monsters of the world.
Many siblings would generally peace out if they found out their brother or sister didn't have a soul, but Dean stood by Sam and made sure he was able to get his soul back. Did it cause Sam to go insane when the walls fell down? Yes, but Dean's heart was in the right place.
Remember when Sam was excited for Christmas but was quickly disappointed when he found out their dad wasn't going to be there? Dean took it upon himself to get Sam a gift -- though he stole it but it's still the thought that counts.