From the sources I've seen on the subject, there appear to be mixed opinions among readers, and among those in the comics industry, on the work which Canadian artist/writer
Todd McFarlane produced in his time at Marvel Comics during a nearly four-year period. Having been a reader throughout those years, I remember my interest waning not long after his new
Spider-Man series was launched in the fall of 1990, a book he would produce as both artist and nascent writer. (Though it bears mentioning that the early 1990s presented me with a
number of books which had me questioning the quality and direction of Marvel's offerings.) In the beginning, however, when McFarlane joined writer Peter David on
Incredible Hulk, I found his approach to be fresh and bold, a unique style for the Hulk that was just as surprising and interesting as that of artist Jeff Purves in the character's subsequent Joe Fixit phase.
McFarlane's time on the title ended after just seven issues, though by that time he had been brought on board Amazing Spider-Man during the run of writer David Michelinie, a gifted scripter and storyteller. (Michelinie would also later compliment McFarlane as a talented storyteller he was pleased to be partnered with.) Like many before him, Michelinie gave Peter Parker his share of ups and downs--a certain Christmas Eve being one of the latter instances, surely.
Reportedly feeling dissatisfied at the lack of control over his work and wishing to have more of a say in the direction of stories, McFarlane was appeased with his own Spider-Man title where he would have creative control--coming into the project as a profitable talent for Marvel and taking a turn toward a future for himself that was his to chart. Yet it was a run that would last just a little over a year, which saw McFarlane eventually develop more dissatisfaction in regard to his differences with editors on story and character direction as well as artistic choices for heroic characters that would have done the Marauders proud. By this time, his variant covers were also contributing to the growth of the speculator market which preceded the near-collapse of the industry--while there was also a curious recycling of previous cover styles to coincide with costume changes.
Whether you consider McFarlane's writing at this point in time to be compelling and entertaining is a valid debate to have, with McFarlane himself weighing in on the fact that he was just beginning to dip his toes into the field. In his later work for Spawn, published by Image Comics, he eventually (i.e., after an early rough patch) came into his own in that regard; but though riding a wave of popularity at the time of Marvel's release of a new Spider-Man book, and showing promise in his first issue, it became apparent over the course of the run that the strength of his artwork wasn't supported by equally robust storytelling for a character we were growing increasingly unfamiliar with.
Following his exit from the book, McFarlane would go on to join Rob Liefeld, Erik Larsen, Marc Silvestri, Whilce Portacio, Jim Lee, and Jim Valentino to found Image Comics, a company not without its own problems but which would turn out to be a stepping stone for McFarlane to even greater exposure and profitability, steadily establishing a media empire for himself which exists as a testament to his persistence and drive as well as his obvious affection for comics. You might find informative a 2000 documentary on the man produced by Kenton Vaughan, with appearances by McFarlane as well as industry peers; in addition, there's a column by David Wallace which covers most if not all of McFarlane's growth in the comics field. The opinion that McFarlane's best overall Marvel work can be found in his partnership with Michelinie in ASM is one that I agree with--but I found myself pleased to see how he built on his beginnings to excel in his chosen field, and remarkably so.