Thaddeus's comment got me wondering about what exactly is the difference between Marvel's Ultimate universe (Earth-1610) and the Cinematic universe (Earth-199999)? After all from what I've seen of the Marvel movies (admittedly not all of them) they seem to largely draw from the Ultimate universe anyway.
The most obvious differences would be that 199999 lacks all of the characters whose movie rights are owned by other studios instead of Marvel, and thus will never show up in the 199999 universe despite existing in 1610 so long as other studios hold the rights. While the exact details of the movie right deals have never been revealed, a number of people supposedly "in the know" have said that the rights are renewed so long as the studios continue to actively develop movies for each character. So, so long as Fox continues to work on X-Men movies, Fox will continue to own the rights - blocking Marvel from using their own characters in the 199999 universe.
Of course with the lack of these characters existing, their back-stories and interactions also never existed.
Screenrant lists the movie rights as the following (Note that not all of the characters listed below exist in the Ultimate/1610 universe - I'm just copy/pasting to be complete):
Reverted back to Marvel
Weird Special Cases
There are obvious similarities in the universes, mainly because both have "realistic" approach to the characters, and there are only so many things you can do with characters and their origin strories without completely changing them. However there are also many differences: The biggest ones are maybe Captain America and Thor. In the ultimate-verse Cap froze after a fight with an alien shapeshifter (chitauri) nazi, and Thor instead of being a noble warrior is a sort of hippie-messiah-cult leader who is also somewhat mentally ill, and has his powers even without his hammer. For the most of the first two volumes of Ultimates it was left to reader to decide wether or not he is a god, or lunatic. Eventually it was confirmed that he is a god reincarnated as a man. Also Iron Man of the Ultimates is a latino named Antonio Stark, Black Widow is his lover who also gets an armor before being revealed to be a traitor who killed Hawkeye's wife and children and joins the Anti-USA -group the heroes fight. Quicksilver and Scarlet Witch who are not only brother and sister, but also lovers were also part of the team during the chitauri invasion, as well as Giant-Man and Wasp.