First, I'd like to state (even though it's irrelevant to the topic) that even at this point in time, Haku was NOT stronger than Kakashi. The hoax to save Zabuza just made it seem like it was so.
Secondly, we CAN'T rule out that Madara somehow trained Obito.
Not only do they know of each others existence, but they have BOTH shown the ability to control the Kyuubi. If Madara did indeed train Tobi, then being able to control the Kyuubi should be of no surprise.
Let's compare the time span of Obito "sucking" to Naruto training during the time-skip.
Obito-Uchiha clan member that already knew how to do elemental recomposition before becoming a Chuunin as seen here...
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Look at the order of the pages if not just re-read the manga to see that he learned something MOST Genin couldn't do.
Then he becomes a Chunin and gets crushed by a rock. This ends the "Obito" we knew and he becomes Tobi, but he had SOME talent before he died. Meaning he had something to bring out.
Now take Jiraiya for instance training Naruto.
Naruto left for two and a half years. Learned Rasengan before that, and under life-and-death circumstances, used it against Kabuto.
He comes back to Konoha at the beginning of Part II with more tactics, a bigger Rasengan, and a as of yet unexplained jutsu. NOT super impressive, but nonetheless he is quite a bit stronger than his peers in Konoha by this time. He has the legendary Sannin Jiraiya for his teacher, who was not born during the time Madara was.
Go back to Obito. He has Madara as a teacher, who has the Sharingan. Obito has the Sharingan. Obito has a master of the Sharingan TEACHING him how to use his Sharingan. He learns to control the Kyuubi and unlocks the Mangekyo Sharingan.
Training with Madara is probably the Naruto equivalent of training with King Kai in DBZ, while Jiraiya would be like.... Master Roshi.
