I can't see it either. And you know why? Because Thor doesn't need it. The norse mythology is rich enough for one movie, thank you very much. Besides that, when you pick a character from some specific culture or mythos, and mix him with a non-related culture, chances are, you're in for camp storytelling.
Imagine a native american indian god (or whatever they used to worship) showing up in the middle of that battle in Troy, fighting Achiles or Hector. That would be so campy. The same could be said of Hercules showing up in Asgard. To decontextualize a character is the easiest way to make him campy.
They did it in the comics? Besides comics being another medium, the comics creators have to bring a new threat to our heroes every month, for decades. There comes a time when all the villains/situations from the hero universe are too tired, and then they have to try something different. That's why we had, say, the X-Men in space, with the Shiar Empire. Or Hercules in Thor comics.
It's not that different from what happens in horror movies. When there's nothing new to tell about Dracula in Victorian London, you put him in space ("Dracula 3000"), in the Old West ("Dracula vs. Billy the Kid"). Or you have Jason in Space. Or a giant Frankenstein monster fighting dinosaurs in a japanese movie. Things like that. Better yet: in the 1940s, when Universal was running out of ideas for its monsters, they started making films featuring Dracula, the Frankenstein monster and the werewolf together. The result was a lot of lackluster movies. They were forcing some characters who had nothing in common (besides being Universal monsters) to coexist in an artificial universe. The storylines didn't feel natural. Now, if you try to read "Thor" and "Hercules" where I wrote "Dracula" and "Frankenstein", you get the idea.
What I'm trying to say is that putting Thor and Hercules against each other in a Thor movie is as artistic, creative and intelligent as putting their action figures to fight in your backyard when you're 8 years old. Plus, it would feel like some cheap, made for TV special.