I'm a huge fan of Mulder and Scully. I think they fall into the "Friendship" category of romantic partners rather than the "Knight and Damsel in Distress" or "Instant Attraction" categories. (There are more categories, but the last two are the ones that popped to mind.)
For example, although Mulder does sacrifice himself for Scully, he also plays Mulder as rather remote. Mulder cannot live without Scully, and his enemies know that. But at the same time, he will never fully commit, never get too close, never (really) admit any consuming need for Scully (I'm referring specifically to Seasons 1-6). Duchovny often plays his feelings for Scully "off" or sideways. I don't know if this is Chris Carter. I suspect not. I suspect it is Duchovny.
And I think this is fairly clever. The point, for me, of the Mulder-Scully relationship is that the final "I love you! I love you!" confrontation is unnecessary because they have already been living a "marriage" for most of the seasons. Their relationship is the relationship of people who are so far gone in terms of intimacy with another human being, Mulder's "Back off!" signs are completely pointless. Which will not, of course, stop Mulder from putting them up. And Scully is willing to put up with Mulder putting them up. Which consequently gives the relationship more edge, more reality, than most romantic TV relationships.
*My favorite indication of this "offness" coupled with reality is in "Memento Mori" when Scully tells Mulder that she has cancer and instead of getting maudlin, he says, "I refuse to accept that." I LOVE that line: "I refuse to accept that." Somehow, it makes Mulder so much more real and more passionate than the usual romantic hero and yet, at the same time, gives you a sense of Mulder's remoteness. (Mind you, that sort of inaccessibility is great to watch on the screen but not so great to fall for in real life.)