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):
20th Century Fox
- Fantastic Four: Doctor Doom/Victor von Doom, Human Torch/Johnny Storm, Invisible Woman/Susan Storm, Mr. Fantastic/Dr. Reed Richards, The Thing/Ben Grimm, Nova/Frankie Raye, Alicia Masters, Willie Lumpkin
- X-Men Mutants: [Agent Zero/Maverick/David North], Angel/Warren Worthington III, Arclight/Phillippa Sontag, Beast/Dr. Henry Phillip “Hank” McCoy, [Blob/Frederick J. Dukes], [Bolt/Christopher Bradley], Callisto, Colossus/Piotr Nikolaievitch Rasputin, Cyclops/Scott Summers, [Deadpool/Wade Wilson], Emma (Grace) Frost, Jean Grey/Phoenix, Juggernaut/Cain Marko, Gambit/Remy LeBeau, Glob Herman/Herman Gardner, Iceman/Bobby Drake, Jubilee/Jubilation Lee, Katherine “Kitty” Anne Pryde, [Kestrel/John Wraith], Lady Deathstrike/Yuriko Oyama, Leech, Magneto/Erik Magnus Lehnsherr, Mastermind/Jason (Wyngarde), Multiple Man/James Arthur Madrox, Mystique/Raven Darkholme, Nightcrawler/Kurt Wagner, Phat/William Robert “Billy-Bob” Reilly, Professor Charles Xavier, Psylocke/Elizabeth “Betsy” Braddock, Pyro/St. John Allerdyce, Quill/Max Jordan, Rogue/(Anna) Marie, Sabretooth/Victor Creed, Sebastian Hiram Shaw, [Silver Fox], Siryn/Theresa Rourke Cassidy, (The) Spike, Storm/Ororo Munroe, Wolverine/Logan
- X-Men Non-Mutants: Drake Family (Steven, Madeline, Ronny), Grey Family (Dr. John, Elaine), Henry Peter Gyrich, Robert Edward Kelly, Dr. Moira Kinross MacTaggert, Dr. Kavita Rao, William Stryker, Bolivar Trask, Warren Worthington II
- Spider-Man: Spider-Man/Peter Parker, Doctor Octopus/Otto Octavius, Green Goblin/Norman Osborn, (New) Green Goblin/Harry Osborn, [The Lizard]/Dr. Curt Connors, Sandman/Flint Marko, Venom/Eddie Brock Jr., Betty Brant, Dennis Carradine (Buglar), J. Jonah Jameson, Ben Parker, May Parker, John Jameson, Joseph “Robbie” Robertson, Gwen Stacy, Mendel Stromm, Flash Thompson
Reverted back to Marvel
- Daredevil: Daredevil/Matt Murdock, Elektra (Natchios), The Kingpin/Wilson Fisk, Bullseye, Jack Murdock, Karen Page, Ben Urich
- Elektra: Christine Cord/Tatoo, Typhoid Mary/Marry Alice Walker, Kirigi, Stick, Stone
- Blade: Blade, Deacon Frost, Dracula/Vlad Tepes, Hannibal King, Abraham Whistler
- Ghost Rider: Ghost Rider/Johnny Blaze, Blackheart/Legion, Phantom Rider/Carter Slade, Abigor, Gressil, Mephistopheles, Wallow, Barton Blaze, Roxanne Simpson
- Punisher: The Punisher/Frank Castle, Jigsaw/Billy Russoti, Microchip/Linus Liberman, Joan the Mouse, Maginty, Mr. Bumpo, Spacker Dave, The Russian, Maria Elizabeth Castle, Detective Martin Soap
Weird Special Cases
- the mutants Quicksilver (Pietro Maximoff) and Scarlet Witch (Wanda Maximoff) were specially allowed to appear in The Avengers: Age of Ultron so long as no mention was made of their traditional mutant background.
- Spider-Man's rights are still technically held by Sony, but in February, 2015, Marvel and Sony came to a special agreement in which Spider-Man would be allowed to appear in the MCU, and the Sony Spider-Man movies would get (yet another) reboot. Under the new agreement, Marvel gets creative control over the character, and Spider-Man and Marvel-controlled characters can cross studios, as new Spider-Man movies are part of the MCU.
- The Hulk's movie likeness rights have reverted to Marvel, but Universal Pictures owns the distribution rights to any stand-alone Hulk movies.
- Skrulls rights are owned by Marvel, but rights to the Super-Skrulls are owned by Fox.
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.