Looking back, it seemed to me that most designers were obsessed with making 'realistic' games, trying to somehow 'fix' Dungeons & Dragons by making the rules more complex. And in RPGs, realism kinda sucks. You want rules and systems that are thematic for what you want to achieve in the game, not to create a simulation of reality.
Conspiracy X is very much a game of the 1990's. Lately, someone suggested that we play it. I own most of the books of the first edition, and I have run a game in it too. It is ranked number 257 in the list -- just above the second edition of Das Schwarze Auge. If you know DSA, that's... telling.
The setting is "X-files with the serial numbers filed off". PCs are government agents (FBI, NSA etcetera) that are part of Aegis, a secret conspiracy. But Aegis is a benign conspiracy: it aims to protect humanity from one of the several other conspiracies that have various nefarious purposes. Using the authority awarded to them by their 'day job', the PCs aim to uncover what is really happening.
And what is really happening is that there's basically aliens and psychics everywhere. Anything that ever happens is sure to be part of the conspiracy. Either it's the aliens (Greys, Saurians, Atlantians) or some psychic running amok -- there's always something sinister going on.
The scenarios are all basically clue-trail adventures where the PCs uncover what's going on by conducting interviews with eye-witnesses to some strangeness and other types of investigations. That's great to watch on TV, because you see what the characters in the TV series see and you uncover the "truth" along with them. But as a scenario, it's... not so good. If you miss your roll to find a vital clue, then that's basically it. Call of Cthulhu has this problem too -- another game that can simply grind to a halt because of a missed 'Use Library' roll.
Which means there are two solutions: either you simply give the players the clues they need and hope they figure it out, or you put them on a railroad and simply take them along for the ride. Both do not appeal to me.
And yes, these problems are not unique to Conspiracy X. As noted, any clue-trail adventure suffers from this. But Conspiracy X never solved this. So to me, it seems like it's kinda... bland. Reading the rulebook does not evoke grand vistas of what the PCs will or can do.
But let's be honest -- there is one thing that Conspiracy X did really well: the psychic rules. Remember the opening scenes of the Ghostbusters movie, where Dr Venkman is conducting an experiment with cards with different symbols on it and trying to get into the pants of the pretty student? Those cards are called Zener Cards and they are indeed used for psychic research. If you play a character with a psychic ability, the GM will draw as many cards as your character's psychic rating (so if you have a rating of 2, that's two cards drawn). You then name a symbol, and if the symbol you picked is among the cards that were drawn, then your action succeeds. It's pretty fun, but it kinda breaks the flow of the game.
I wrote that I ran an adventure in it, and it offered one of the highlights of my GMing career to date -- but that was not because of the game.
About a year before I ran the game, there was a police case in the news about a Winti practicioner from Surinam who had some 'voodoo dolls' that turned out to contain mummified baby bodies. I had collected newspaper clippings about the case and fabricated a scenario. Then I made sure that everthing the players discovered was consistent with the publically available information -- so when I gave them the second newspaper clipping, one of the players remarked: "Yeah, we already knew all this stuff!" And then he realised he was holding a clipping from an actual newspaper, which weirded him out. I'm still proud of that.
(The scenario petered out because the players failed to combine the clues in a meaningful way. So it did turn into somewhat of a railroad where the players were like bemused passengers staring at the weird stuff going on.)
The Gumshoe system was designed specifically to adress the clue-trail problem, and it is the underlying system for Trail of Cthulhu, which is coincidentally ranked third in RPGGeek's list. I do not see a Gumshoe game in the style of the X-Files, but that doesn't mean that one of the existing Gumshoe games could not be 're-skinned' to support this. Using any of the Conspiracy X sourcebooks to provide background is easily achieved once a modern system is in place that supports the type of play you want.