I suppose the problem is that the idea of discovery tends to fall under the category of science fiction, for reasons that you can surmise. But it could be incorporated into many other movie genres and be quite successful. Consider something like the exploration of the newly discovered WW2 Japanese mega-sub sunken of the Hawaiian coast. If the airlocks were still intact, who knows what it could hold. The secret is to remain realistic. (As much as possible) No ghosts, no nuclear devices, and no precious metals. (I know I just killed the movie for most.) How about simply proof of a conspiracy by two countries?
What got me going on this thought was an advertisement for Jurassic Park 4. Of course the movie will contain several big names of Hollywood. That’s actually not a good thing. I prefer new comers to the screen so that the writers have to build a better premise. The only exception is that it must include Sam Neill’s character. (Which it won’t) He’s the dinosaur man for crying out loud! And for me, the only thing that keeps the movie afloat, because (for his character) it is all about understanding the discovery and how you never own it; not about being eaten by the discovery.
Another movie of discovery is The Last Days onMars. Sure there have been other movies about the exploration of Mars, but it doesn’t necessarily make it sci-fi. With the MARS ONE program propelling promptly forward, we definitively have a timeline for humans to walk the planet. (It’s going to happen people!) Moreover, discovery is inevitable. The actual MARS ONE colony will be beyond our control and imagination. It will be televised as the ultimate reality show. So a film such as The Last Days on Mars comes much closer to documenting that something unknown.