I'm actually torn on this. At first, I think the same thing, but then I think of the threats that the JL has faced in recent stories. There is nothing light-hearted and comic-like about some of these guys. From the Secret Society to Doomsday, Darkseid, and the Anti-Monitor these are all very dark and gritty characters that could fit within a universe where alien life is well established through two of our solo heroes. The simple fact that Superman and Green Lantern exist in this universe establishes all you need to open the door to a global threat.
To be honest, I felt the same about The Avengers when they were including Thor. But in the grand scheme of things, in a world with super soldiers, mutant beasts, and ultra-high tech suits of armor a trans-dimensional alien race didn't feel that odd.
I think if you take a step back and consider what we are a accepting in the real world realm with Batman (seriously look at what we accepted in those films as real) and now Superman, and I can see a Justice League concept working itself out. How easy they can make the rest fit in will be determined by how they show Krypton and how they go forward with Batman. The biggest issue Nolan's Batman films created was that they existed in a bubble. The idea of Bane holding Gotham under siege that long without any outside attempts to stop him makes any future superheroes in the same continuity feel...off. They have to make Gotham part of a world, or use that situation to set boundary rules for the JL.
First off, I haven't been following this thread like I should have. *subscribed*
Second is that there are quite a number of plausible explainations why Superman, or even Green Lantern for that matter, couldn't involve themselves in the events of The Dark Knight Rises[Speculation ahead].
- In the first Man of Steel trailer(the pair with Johnathan Kent and Jor-El speaking in the background), we are exposed to Clark to being a wonderer, someone with no purpose in life. He also worked as a crab fisherman, which, if you know your Discovery Channel, the roughest area to fish is off the northern coast of Alaska, WAY too far from what is commonly accepted as Metropolis(New York) and Gotham(Chicago). Sure, you can argue that with super speed, he can get there in a flash, but I speculate that Clark was trying to hide his powers under the advice of the elder Kent(a fact that comes out in later trailers), and making that run would blow his cover.
- Let's say that even if Clark gets to Gotham, he would have been no help to the police as a fundamental power that would have been useful in finding that bomb, x-ray vision, would have been rendered useless by the fact that all three of the trucks were lead lined. As you know by that broken arm that you may or may not have gotten in the third grade, x-ray radiation does not penetrate, you guessed it, lead.
- Hal was on Oa for a length of time for boot camp as a lantern.
That is just three examples.