Yet they were very quick to drop the Narnia series after the 2nd movie didnt make as much as the first
Because they saw that the Narnia franchise would have continued to decline, even if they moved it back to a more appropriate slot. Voyage of the Dawn Treader did slightly worse than Prince Caspian even when it was moved to December, the time when The Lion, the Witch, and the Wardrobe came out. Also, Disney didn't just flat out give up on the Narnia franchise, they offered to make the film, but with a lower budget that Walden Media wouldn't accept.
Also, Disney didn't own the Narnia franchise. Walden Media were the ones who held the film rights (and got a share of the profits and why they were able to take the series over to 20th Century Fox) and the estate of C.S. Lewis.
Meanwhile, Disney flat out owns everything regarding Tron. They don't have to deal with any potential rights issues. They get all of the money in regards to licensing, etc. If someone else owned Tron, I'd bet that Disney would have dropped it faster than they did Narnia.
and they have pretty much said there wont be another stand alone Hulk movie.
No, Marvel Studios said that there won't be another stand alone Hulk movie for the time being. That decision was made well before the Walt Disney Company bought Marvel Entertainment. And with Marvel Studios' plate being full with Captain America: The First Avenger, Thor, Iron Man 3, and the Avengers (along with trying to find ways to get smaller characters out there), there is just no room for another Hulk movie for the time being until after the Avengers comes out.
But please note that Disney hasn't given up on the Hulk. They have ABC Studios developing a Hulk TV show, a decision that was made after Disney bought Marvel. And if that show is a success and if audiences like how the Hulk is portrayed in the Avengers, don't be surprised to see another Hulk movie in the future. Disney still sees the Hulk as a viable franchise.
They may be a bit better than other studio's but it doesnt mean they are all that different from them. I hope they do make another Tron movie as I thought TL was great, but I aint getting my hopes up.
Another Tron movie certainly isn't guaranteed, I think that Disney still wants to gauge how Tron: Legacy does on home video, but I don't think that Disney is willing to give up on the franchise just yet. Mostly because they own the license flat out and stand to make money by keeping the franchise alive beyond just movies, and Disney is more lenient than Warner Bros. (which is also dependent on licensed franchises like DC Comics, Harry Potter, etc.), Universal Studios, etc.