Marvel was privately held for most of its early history. In 1986 Marvel Entertainment Group was purchased by New World Entertainment, who sold it again in 1989 to MacAndrews and Forbes, owned by Revlon executive Ronald Perelman. In 1991, Perelman listed the company on the NYSE via a float underwritten by Merrill Lynch and First Boston Corporation. The first report was the Third Quarter 1991 report.
The Quarterly reports (1Q, 2Q, 3Q) tended to be four-page summaries, while the Fourth Quarter (Q4 or Annual) Report Delivered a more detailed report of the company's standing through the year. It is these Annual reports that tended come in the form of full-realized comics combined with highly-detailed text akin to a more traditional Annual report.
The company produced Quarterly and Annual reports until 1996 when the company filed for Chapter 11 protection. The 1996 Second Quarter Report was the last from this period. Emerging from Chapter 11 protection in the early 2000's, the company again produced annual reports starting from 2003.
The 2006 annual report was the last to feature any comic-style artwork. The 2007 and later reports were plain old text reports just like any other company. Disney purchased Marvel in 2009, and annual reports are no longer produced.
What truly makes those earlier Annual Reports great is that you have Marvel heroes duking it out with Marvel Villains while spouting facts and figures about the company's record growth... fictional super-characters discussing super-expansion which was later revealed to be also at least partly a product of wild imagination.