Arson Welles
is the lightning
I know he's gonna be in Guardians breh, however his role in The Avengers should have been bigger and he should have cameod or been referenced in Iron Man 3 somehow or someway, Marvel Studios biggest two movies, movies that people were always going to watch, it would have got people talking about the character. Also from what i've heard he's not even going to be the main villain or a main character in Guardians of The Galaxy, it's going to be Del Toro and some other character called Ronan,.Thanos will be in a background/minor character, it's all about screen presence, that's what gets people talking about villains, Thanos currently has none of that at this moment in time, you can get away with it with an inconic villain that everyone knows about, however Thanos isn't.
Anyone who has read Marvel comics within the last 5 years (and EVERYONE who has read them in the last 10) knows who Thanos is.
Thanos was in a major arc in 2010 called "The THANOS Imperative". http://en.wikipedia.org/wiki/The_Thanos_Imperative
Thanos was the main villian in "The Infinity Saga" which many people believe to be one of the best arcs in Marvel. Ever. http://en.wikipedia.org/wiki/Thanos#The_Infinity_Saga
Thanos has a wicked helicopter with his name on it, and he uses out dated curses when flying it around.

Thanos DATED Death. Like the physical manifestation of Death. - "Thanos had become fascinated with nihilism and death, and worshipped and eventually fell in love with the physical embodiment of death, Mistress Death, albeit under a different name and appearance. Committing several horrifying acts at her command, he was doomed to a future of destruction and hate. As an adult, Thanos attempted to create a new life for himself, by starting a family and supporting them by joining a crew of vicious space pirates. One day however, Thanos was visited again by Mistress Death and gave into the temptation she posed. He murdered his family and took command of the pirate crew and set off to his old homeworld of Titan."
Basically, the dude is a huge player in the Marvel universe, and to say that people don't know/aren't excited to see him, is wrong.