There's a BUNCH of Marvel heroes ripe for tapping into the Halloween film market. With Ghost Rider leading the charge. And whether you like GR or not, it STILL beat the living crap out of many other recent so called "Halloween films" at the box office, such as 30 Days of Night, and Rob Zombies Halloween...
Aside from GR, there's lot's more supernatural Marvel characters that could be brought to the big screen:
Dr. Strange
Moon Knight
Marvel's Dracula
Werewolf By Night
Daimon Hellstrom
Man-Thing (done better)
The Living Mummy
The Darkhold
Satana
The Gargoyle
Dr. Druid
Brother VooDoo
Simon Garth
Devil Slayer
Elsa Bloodstone
Lilith
If a relatively unknown character like Blade can be made into a successful 3 franchise film, certainly any one of THESE characters can as well, with the right script.