Different Universes. Ultimate Spiderman belongs to the "rebooted" Marvel Universe called the Ultimate universe. In the Ultimate universe Spidey is about 15, all the X-Men are teenagers (except Wolverine), and the Avengers are called the Ultimates. --- "That's real kung fu! I hope you learned your lesson."
Ultimate Spidey is also somewhat weaker in some powers. His spidersense, for instance, warns him of danger, but not the direction of it like Amazing Spidey's does. I think I like Ultimate Spiderman more than 616 universe, due to all the newer storylines. Green Goblin being a huge hulking beast, Eddie Brock being his child hood friend, etc; I feel more emotion in those comics and I can connect with the characters easier.
Earth-1610 (the universe of the Ultimate Marvel comics) is different from Earth-616 (the "normal" Marvel universe). Most Ultimate characters are significantly different from their 616 counterparts.
Ultimate Spidey's not too different, though as mentioned, his abilities are weaker. --- We're whalers on the moon! We carry a harpoon! But there ain't no whales so we tell tall tales and sing our whaling tune!
Ultimate Spidey is a younger version from a rebooted universe that attempts to be more modern and relatable but usually just ends up like a Clunky terrible Image comic and everyone hates it.Ultimate Spidey is significantly weaker than 616 Spidey but he has the distinction of being the only one of those comics not written like complete garbage
Poor Parker kid.He deserves better --- The [OSMBV] Harbinger of Newbie Death Reigning Sorcerer Supreme of the GameFAQs dimension
Ultimate Spidey was a great comic, I swear I hate Joe Quesada for ruining the Ultimate universe (among all the other crap he's done). --- "Remember, there might be some momentary discomfort" ~ Mr Freeze
Also his villains were a lot different from how they used to be. What with Ock becoming closer akin to Magneto now. --- "Ragna the Bloodedge... is already MY HUSBAND!" - Noel Vermillion "WHAAAAAAAAAAAAAAAAAAAAAAAAAAT?!" - Ragna after the above statement