The writers for Ultimate Spider-Man wanted to have a plot line about the Sam Raimi/Toby Macguire movies existing in-universe, but they weren't sure if they were legally allowed to include the movie version of Spider-Man in the comics. Instead, they had the plot be about Sam Raimi and Toby Macguire working on a Spider-Man knockoff movie, Arachnoman. Eventually they found out that they could legally use the movie version of Spider-Man and re-released the comic with Arachno-Man replaced with Spider-Man. An Arachno-Man costume is also unlockable in the Ultimate Spider-Man game, and you can find an Arachno-Man poster.
I've never seen the original version of the comic (USM Vol 1 #54), if anyone has it I'd be interested to see how exactly it differs from the final version.