Okay, the deal is this. If Nathan Fillion does Uncharted: The Film, then one of two things will happen.
A: It'll do badly in the box office, yet fans will love it, it'll be a cult hit, and will sell millions of DVDs, making it a success overall. Or...
B: It'll be a megahit and will be one of the most successful video-game movie adaptations of all time.
Because you know, that's generally how Nathan Fillion's projects work out. Although that may be linked to the fact he's worked on a fair few Joss Whedon projects, which also go that way (usually Route A aside from perhaps Angel and Buffy...), so this may be a mixup and if so then just disregard everything I just said.
Either way, from the little I know of the games, and the lots I know of Fillion's considerable acting skills and the film-making skills of David O. Russell, this looks like it could well be really, really good...