One thing Chris Carter got right about his series: that Mulder expelled himself from social living because he is different. And Scully got also excluded because she supports him at heart but, ironically, none of his beliefs. This was more important than conspiracies and UFOs, it was the core of X-Files: She always had to believe, but wouldn't.
And now they are together as lovers, they can't live without the other one but at the same time Mulder's compulsions are unbearable, "write a book" she says. It's depressing, they will never be happy: Mulder will never decease to be Mulder and Scully can't live with or without him. And past all these years they still struggle with their relationship, not sure if it was the right path, that only a supernatural "don't give up" may change.
Another gloomy part was Mulder talking briefly about his sister, that in 2000's his UFO beliefs are ridiculous as Santa traveling the sky. Mulder changed. He doesn't argue back. Not even a wisecrack. He is not so convincing anymore because looks so defeated as a Unabomber cliché. Its the Mulder helpless and without a badge. So he is hesitant, fearing the failure, wanting to be back in FBI investigations but hating the prospect of it.
Meanwhile Scully fights back a real life "church vs stem cell research" that might terminate her medical career. Her maternal side urges to save a boy that she never had or will have. She even fights the parents for his life revealing her as True mother in Salomon's sense. And Mulder is just not there, almost as if he doesn't care.
This is the canvas of I Want to Believe, everything else are cumbersome devices trying to appease the X-Philes that don't play very well in a larger screen: Any given moment a skeptical FBI agent walks away saying "it won't work, let's leave" Mulder has an epiphany saving the entire unorthodox investigation. Every time Mulder is revealing something new, Scully cuts it out until she has an epiphany herself. The audience can anticipate every plot move like a series rerun.
The X-files tune playing at the portrait of W.Bush suggests that Mulder and Scully doesn't have a place in FBI; of coursely, surely, after all, all Conspiracy Theories are very practical under the W.Bush doctrine. But the conspiracy motif that anchored the series were only explored in this silly moment; instead of the bigger-than-life "oh, the humanity" moment, the movie goes for a CSI case that doesn't redeem Mulder nor Scully a bit. The movie ends with a reticent acceptance that is all there is and their kiss is almost a manifestation of that. Is terrible to see two close friends of mine unhappy for life in the middle of the cold nowhere; their love for each other is virtually a curse.
