The main competition for DC Comics, Marvel is a comic book publishing company that created many iconic superheroes. Recently Marvel has been milking their creations for all they're worth by making movies for practically every character they have. Some of these movies (e.g. Iron Man) are better than others (e.g. Spider-man 3). Average abilities in the Marvel universe are superstrength, superagility, and superspandex, and the fact that you only need pretty much to add water to get artificial intelligence. (Source)
- Marvel is the strongest universe in fiction, as it not only possesses a huge amount of cosmic reality warpers, it also has wide range of power, powers are ranking from normal human to omniversal level like Living Tribunal or The One Above All, one of the few true omnipotents in fiction,...they often used by many manga fan to against their favorite character. However, many people use movie or animated version, which is far weaker than comic counterpart and non-canon.
- Another reason for it being so powerful is that the Classic tier, people in this tier are the one above Living Tribunal like Beyonder, Molecule Man, Heart of The Universe,...all of these characters are capable of omniverse-busting, also Marvel was once below DC until these guys appeared and pulled them to the "top" again. At the current time, almost no fiction has nigh-omnipotent characters who stand a chance against them.
- Also, don't forget: Squirrel Girl.