I'd like to see more of a crossover between Marvel villains. Doctor Doom in X-Men and Magneto in Avengers. And no, I'm not counting Children's Crusade because it ships only when the seasons change.
That, and in that story, Magneto is not a villain in any way. In fact, he is the most compassionate and rational adult character in Heinberg's entire mini so far. The rest of the Avengers? Homicidal maniacs (Wolverine), general "hit/zap it" grunts (Iron Man) or characters who should know better but do as they're told (everyone else but Wonder Man). Not even Spider-Man is willing to let out a, "hey, maybe we shouldn't allow Wolverine to execute a 16 year old boy in front of us" sort of line.
But, in all seriousness, does Marvel have any villains who draw a crowd? So much of one that they do so outside the titles in which they are known best? Because I don't think villains have drawn much of a crowd at Marvel for ages. Marvel promotes many things for events, but I think the crowd is there for creative team and "importance". Marvel went from 2006-2008 having events in which heroes punched each other (Civil War & World War Hulk - yes, Hulk is seen as a hero by the masses). I think this era was the demise of the audience giving two ****s who the villain is, aside for rare examples. By "the audience", I mean the silent majority of non SHH members who buy comics and make up 90% of its audience.
I'd argue the biggest villains, by obligations to other books, CAN'T show up and do ANYTHING of "importance". Let's think of some big villains. Norman Osborn? He appeared before, and he's in lock up. Presumably, other writers want to handle him, and Marvel is probably giving him a rest after DARK REIGN. Like Skrulls, and Deadpool, he's been played out. Loki? Fraction made him a kid, and not a villain yet at all, in THOR. He's out of play. The Hood? He showed up, but otherwise stated, he can't do anything of consequence. He's Bendis' villain. If any team defeats him in a relevant story that "counts", it is not going to be the third string Avengers book, sadly.
There was a moment when Osborn/Iron Patriot and Sentry were totally spanked by the Young Avengers in trying to apprehend them in DARK REIGN: YOUNG AVENGERS, and afterward, he literally faced them and said, "This didn't happen. It doesn't count." The irony is Cornell was probably breaking the 4th wall a little, and he may not have known it.
Other big villains. Kingpin? He's been attached to AMAZING SPIDER-MAN, lately; although to be fair, Slott and Gage are frequent collaborators and often share their toys with each other. I don't think Fisk is that big anymore; Marvel has spent years stuffing him into the sidelines for Hood. Red Skull? Dead, and his daughter Sin is the property of Brubaker in CAPTAIN AMERICA and Fraction in FEAR ITSELF.
That leaves Ultron, who last showed up not long ago in MIGHTY AVENGERS. I suppose his subplot with Jocasta remains unresolved; Pym basically arranged a stalemate instead of outright defeating Ultron. But is he as hot as he was when MIGHTY AVENGERS #2 sold? When Bendis and Cho turned him into a naked woman? I don't know. MIGHTY AVENGERS sold better than ACADEMY has after a year, but it also was the Avengers' B-title, and Slott could be a bigger name. ANNIHILATION CONQUEST did not sell as well as ANNIHILATION did; prompting editorial, I imagine, to "suggest" that Abnett & Lanning resolve Brubaker's old X-Men plot with Vulcan and amp the Inhumans, which produced the better selling WAR OF KINGS. Vulcan > Ultron, at least in terms of sales. I'd probably rather the kids have this exact same moment against Ultron rather than Korvac; you could argue that besides the time travel power thing, you could swap Jocasta for Carina and the tone of the story would work properly. You wouldn't have the "Future Cadets" moment, though, and Ultron may be too big a villain to "extinguish" right now - while no writer is really going to miss Korvac. Plus, at least to Avengers fans, Korvac remains one of those rarely defeated villains; he just shows up so rarely, they may be the only ones psyched for him. I get it, and I do think Korvac offers far more of a challenge than Ultron; Ultron's just scarier. Korvac is a glowy, screamy energy man - the Collective, only decades sooner.
Baron Zemo? Property of Brubaker and/or Fraction on aforementioned titles. Besides, according to some Hype members, he's actually an anti-hero who has been written poorly this last year, so having him do anything that isn't saving orphans from fires is unholy rubbish. So, Zemo's out. And most of the REAL Masters of Evil have become proper heroes in Thunderbolts (Techno, Songbird, Moonstone), or are in limbo after doing so (Radioactive Man, Atlas).
To Gage's credit, the Sinister Six are slated to appear in AVENGERS ACADEMY #14, judging by the cover. They may be about as good as one can get.
I agree that promotion is key but writers don't much affect that. They're job is simply to write. And really, has anyone EVER begged to see the Hood? Marvel's problem is they've taken every key villain that DOES drive sales and ****ed them out as much as the heroes. I mean, I remember back when I saw that Magneto was going to show up somewhere and I got excited... same with Dr. Doom, Liki, Green Goblin, and others. Nowadays we have Doom showing up in 2 or 3 books at a time and somewhere almost all year long. Who cares if Doom shows up again?
No body cares about heroes or villains enough to buy guest star issues with them because they can just go somewhere else that they're already reading and read them. But when you have people like me, on the fense with the book, a fight with Doom or the Rhino, or someone who is likable, might keep me on for a few more issues than someone I've never read before. Now here I am dropping the book when I could have stayed with it for this arc, and hey, maybe the Fear Itself tie-ins would have pulled me in too. But now I won't be getting either because of Gage's choice of villain.
(A lot of my post above was partly for you.)
You'd honestly buy an issue with the Rhino in it? You'd be the first.
The Rhino is a typical thug sort of villain. He's better known than Mentallo, but he's also not usually the one who draws a crowd. He keeps getting used in "test a new hero's mettle" stories, and his losses add up. To be fair, he was the first villain the Kevin Masterson Thunderstrike fought in his mini, and Rhino actually won. But, you didn't see anyone flock to that issue.
In the same breath as you dismiss Dr. Doom appearances, you also want to see him in this book. The problem, though, is Doom as big as he used to be? He's been off the big stage for ages. He's better known than Whirlwind, but, he is also the "property" of Jonathon Hickman's FF right now. He's out of play.