Technically speaking, the Transformers characters were created by Takara Toys in Japan but the Westernized versions of the characters were developed by Marvel's editor-in-chief at the time Jim Shooter, and Marvel writers Dennis O'Neil and Bob Budiansky and was, at the time, in canon with the Marvel Universe. G.I. Joe, as our generation and every one since knows them, was created by Marvel writer Larry Hama, who originally used a treatment he had for a spinoff of Nick Fury as the backbone behind the then-revamped line.
So . . . yeah. There's a reason Marvel's called The House of Ideas, and Hasbro benefited greatly from the company's input in two of its longest-lasting toylines.