I think that any character that starred in the 93-97 Animated Series has to be considered an A-lister. Especially if they've been in 2-3 of the films. I would break it down like this. At this current time, not ten years ago, not in 2005, right now, it's probably similar to this, in terms of popularity, exposure, and 'coolness' factor:
A-Listers:
Wolverine
Professor Xavior
Cyclops
Jean Grey (yes, she's still dead, but her exposure in the series and films, but her Phoenix alter-ego, will always keep her in the A-list)
Storm
Rogue
Iceman
Magneto
then, to a lesser extent:
Beast (seems to fall to the sides a lot)
Gambit (the '93 series helped Gambit a lot, but that's the only factor keeping him A-list)
Nightcrawler
Colossus (Astonishing keeps him A-list)
Shadowcat (Astonishing keeps her A-list)
Emma Frost (rising up the ranks ever since Morrison)
Mystique
B-Listers:
Psylocke
Angel
Jubilee (overall suckiness aside, people know who she is)
Jamie Madrox (Madrox and X-Factor have given rise to his popularity)
Layla Miller (her inclusion in House of M and her wicked personality have made her the only other X-Factor member to stand out outside of the title)
Polaris
Havok
X-23 (some would say she's an even better character than Wolverine. I agree)
Marvel Girl (ew)
Bishop
Cable
Juggernaut
Sabertooth
then, to a lesser extent:
Scarlet Witch (yeah, she's responsible for all the mutants losing their powers, but who cares?)
Quicksilver
Cannonball
Blink (for being an alternate dimension character, B-list is pretty damn awesome, though Exiles' decline will put her back in the C-list soon)
C-Listers:
The rest of X-Factor (one of the best titles, but individually these characters don't hold a candle to being as widely known as the ones above)
The rest of New X-Men (also a great book on the rise, and these kids will be X-Men one day, but right now they don't have the exposure)
Warpath
Darwin
Hisako (for a character who barely's done anything, that's not bad - thank Astonishing for her (most likely temporary) rating)
Illyana Raspution (for a long-time dead character, not bad)
Forge
D-Listers:
Husk
Stacey X
Ceceila Reyes
Maggot
Marrow (although if she begins to be featured more, like in her recent X-Factor apperance, she's move back up to C)
Lila Cheny
Slipstream (please, keep him on this list forever)
Lifeguard (please, keep her on this list forever)
Shatterstar
Sage
Dazzler
Longshot
Captain Britain
Northstar
Sunfire
Lady Mastermind
Karima
Beak
Caliban
Wow, I went all out for this. So feel free to agree/argue. I might change and save this list for further reference and debate (I like lists. A lot.)