I like him as you can probably tell from my avatar. He has a good heart, he tried saving Oro like Naruto tried to save Sasuke, he took in Nagato, Yahiko and Konan when he could have left them to fend for themselves since they were from another village. He was comic relief when needed because of his pervy nature. He could also be serious when necessary. One of the best as far as feats in battle, pre all of the crazy power ups. Could have taken down Oro and Kabuto had Tsunade not drugged him. Given a few more minutes to put the evidence he gathered together on Pain and he would have been able to defeat him. He cared about Naruto even though he did not think of himself as the fatherly type. He seemed to enjoy life and did not take himself too seriously.
While he is my favorite, I can also admit he has some shortcomings. Using Naruto's money when he had plenty of his own was not cool. Going out so much and leaving Naruto by himself most of the time, especially not making sure Naruto came back at night to sleep was more than a little irresponsible, especially when he knew people were after jinchuriki's. I guess he was trying to make Naruto stronger but it did come off as being a bit cold at times, especially having been so close to Naruto's parents and knowing he grew up without them.