So apparently J'son is not Star-Lord's dad in the movies.
We'd already written about Peter Quill's parentage in the comics -- and while even that may get tweaked slightly with the character learning about a previously-never-mentioned half-sister in the first issue of the new Legendary Star-Lord ongoing, as far as we know that will hold for the time being.
The decision to change the identity of his dad is arguably not surprising considering that the overt references to Jason and the Spartoi from Greek mythology would have been difficult to explain away without just being redundant to what they'd already done with the Asgardians in Thor.
So...who might it be?
This one would be a big change, and why it's tempting is kind of self-evident. You've already seen two of Thanos's kids, after all.
That said, while everyone immediately started saying "What about Thanos?" when Gunn revealed that Quill's father wasn't J'son, it not only seems unlikely, but putting the plan into place would put director James Gunn very much at risk of being accused of ripping off Star Wars.
A character who's forced into a life of heroism when all he wants at the start is to explore the wonders of space? Check.
The mysterious, powerful villain who turns out to be that lead character's dad? Check.
A sister with whom he shared slightly too much sexual chemistry in the first movie? Check.
And while the Ravagers would be right to call Thanos a jerk (I can't remember the exact insult used so we'll go with that) toward the end of the movie, that's probably an understatement. Also, it would be surprising if they didn't comment on the fact that he was now traveling with his adoptive sister at some point.
Captain Marvel (the original) is another popular choice. Like Adam Warlock (named below), he's got a humanoid form, blonde hair and powers that could given him an external glow, so that line about how Quill's father looked like an angel applies.
In the comic book source material, he's also got connections to Thanos that would help the plot along.
He's fairly unlikely if only because a Kree-human hybrid wouldn't be likely to surprise much of anybody at Nova HQ. The idea that the father is a very ancient, powerful being makes "Kree-Human hybrid" unlikely since both of them are, relatively speaking, common and not all that powerful.
That whole "angel" thing probably fits this character, with a halo and wings, better than just about anyone else.
A member of the classic Guardians, he has also been referred to as the "Giver of Light," which kinda jives with the whole angel surrounded in light motif.
And just about every version of his often-changing costume has featured a star on his belt, suggesting a potential root for the nickname "Star-Lord."
There isn't a lot to suggest that it's Warlock outside of the fact that, much like the candidate below, he would be an ideal candidate as a narrative foil to Thanos. We know that was his cocoon, we're pretty sure he's coming along in the sequel one way or another...so the question now becomes whether they would introduce him to the cinematic universe as his own character or as an extension of Quill by making the two related.
That said, it would give the story ties to the Kree, the alien race that was the focus of Ronan's, ahem, civic pride in Guardians. Adam Warlock has crossed paths with them a number of times over the years.
Starfox might be my favorite candidate on this list, in part because he's so outside-the-box and yet still very plausible.
The brother of Thanos, Starfox's real name is Eros and he's one of the Eternals of Titan. He has a lot of character traits in common with Valiant's Aram "Armstrong" Anni-Padda, including the fact that he spends his immortality in search of little more than a good time.
As noted in the Marvel Wiki, "Starfox can psionically stimulate the pleasure centers in nearby people's brains, making them calm and open to suggestion using his persuasion skill. It has been suggested that when in physical contact, and there is direct line of sight between the subject and the target, Starfox can use this euphoria effect to cause a person or persons to become infatuated with him, objects, or people of his choosing or simply to make others feel good while in his presence."
That could explain the angel surrounded with light thing without getting too literal -- although again, nearly any cosmic being who came down from the sky in some kind of spacecraft might very well fit that description to someone who's never made interstellar contact before and it's difficult to say how much to put on it, exactly.
Again, the fact that he's Thanos's "good" brother would make for an interesting parallel -- and it would also explain both Nova-Prime's remark that they haven't seen beings like whatever Quill's father is around for years and her excitement to do so.
Okay, so this one probably shouldn't be on the list, since there is at least one explicit line of dialogue saying that it ain't him.
Still, it's hard to ignore the relationship they have combined with Yondu's own line about how he "may look like an angel...."