According to Cinema Blend on Wednesday, "Guardians of the Galaxy" movie spoilers reveal something interesting about Star-Lord's father in "Guardians of the Galaxy." There are some possibilities only because Yondu Udonta, played by Michael Rooker, made mention of him after he left Xandar with the supposed Infinity Gem that is highly sought after by Josh Brolin's Thanos. For those who saw the movie, this left things quite open ended as even Yondu didn't think to highly of Peter Quill's dad.
Considering that comic book fans may already know who Peter Quill's father is, the Marvel Cinematic Universe may not necessarily follow the same lineage as their graphical counter part. If they do still follow the "arc" of the comic books, J'Son of Spartax could be a likely choice.
For those familiar with the comic book back story, J'Son of Spartax is actually royalty well versed in many skills, most notably as a pilot. He is a resident of the planet Spartoi and during an intergalactic battle, he crash landed on Terran/Earth, met Meredith Quill, fell in love, and birthed his son Peter Quill. Some may remember the beginning scene where Meredith referred to his father in some kind of divine fashion.
One could only speculate that Yondu Udonta a possibility. Though he was a surrogate father of sorts as he just not only adopted but abducted Peter Quill, a loving father wouldn't necessarily eat another humanoid being, especially if he is the father. Though that could just be all tough talk from Udonta's years of Ravager-like attitude. If one recalls Meredith Quill's final's moments, she did speak of his father as a pretty angel and later in the film, Yondu referred to himself in a similar fashion.
Another possibility could be Adam Warlock. Fans may have already spotted the Easter Egg in "Guardians of the Galaxy" of Adam Warlock's cocoon and once artificially brought to live by Earth's Enclave. He was enlightened to go against his creators and travel into the galaxy where he was beholden the Soul Gem and had a calling to protect the universe. That being said, it's not totally unthought of that Peter Quill could have the same DNA lineage given the ability to wield an Infinity Gem and able to control its power. Also, this could be reaching, but Adam Warlock's cape and Infinity Stone could liken him to an "angel" as well.