Without a doubt it's the comics, Uncanny X-Men. Think about it, without the comics there would be no original cartoon, no Evo cartoon and no movies. They deserve the proper respect, plus if you have only read the comics in past few years you have no idea how good they really were. My collection of Uncanny X-Men has a core with very few missing issues begining at #180 up to #290 with maybe 8 issues missing out of that. Besides that core I also have many clumps of issues I have managed to put together including #'s141 and 142 called the Days of Future Past, one of the best story lines ever done.
No matter how hard they try, no movie or cartoon can reach the level of depth of storytelling or character development that the comics do. I have been collecting comics since Lee and Claremont launched the X-Men title (now New X-Men). I have all of those issues, all XTreme and Ultimate X-Men issues, and all Uncanny X-Men issues since right before Onslaught. It's not the creators fault, it's just your attatchment and understanding of character's cannot be that great from a few half-hour shows or a two hour movie. There's too much people don't know that the creators can't fit in.
For all those here that read the comics, they know. For those that don't, start; it's entertainment at it's best. Also if you haven't read the Gambit and Bishop mini-series, I highly suggest that you do. Scott Lobdell really has a handle on the characters involved, and believe me when I say you will be surprised in what happens.