I think this is mostly true, but some Marvel characters are classics. A Capcom All-Stars won't be the same without Magneto. In fact, most of the flyers in MvC3 are Marvel characters. Outside of stuff like Devil Trigger, Trish is the only traditional 8-way air dash character. Doom, Dormammu, Magneto, Storm, Phoenix, MODOK, Thor, Iron Man, and Nova are the other options.
Morrigan has a 4-way air dash, and Firebrand has command dashes (huge difference). Capcom would have to pull in some serious bias toward winged/magical characters to make a Capcom All-Stars feel like Marvel. Which, you know, practically guarantees Nina. ;-D