I'm an unashamed comics reader (and writer, now that my Starship Troopers strip's been published). I don't read much in the way of superhero stuff, but I certainly don't shy away from it just because it can be silly at times. Garth Ennis' "Punisher" and "The Boys" are on my monthly list, as is Warren Ellis' hilarious "Nextwave".
None of that damages my enjoyment of a good Rifftrax, though. There have been some awful movie adaptations of comics, and they deserve no softer treatment than Cocktail or Crossroads (I'd definitely throw in a vote for "Hulk" getting the Rifftrax treatment). However, there have also been some quite extraordinary ones ("Sin City" and "A History of Violence" spring to mind). I guess I'm a little saddened that there are people who will go and see a "comics movie" who would never even consider reading a comic - as if the adaptation process somehow legitimises the material for them. That, I think, is a great shame. On the other hand, anything that raises the profile of the medium is ultimately a good thing. If one viewer walks into a comics shop after seeing an adaptation then I'd mark that in the "Win" column.
Sorry - rambling a bit. Back on topic: I think X-Men was basically a well made film, with enough points of contact with the source material to satisfy the comics crowd without totally alienating the outsiders. These same factors made it, for me, a decent candidate for a Rifftrax. As others have pointed out, much of Mike and Bill's humour played on factors that most comics-literate viewers have lived with for decades - but once in a while I like to see how things look from the outside.
Cheers,
Cy.