Why is Gene Siskel also not as well regarded as Roger Ebert today?

Siskel was often too nitpicky and thus was more likely to give a good movie a bad review. Ebert could see past a movies minor flaws so I think the viewers appreciated him more.

Gene's reviews tended to be much shorter and to the point. They told you what you needed to know in a paragraph or two and then let you get on with the rest of your life. He didn't attempt some kind of literary masterpiece in every review. I think there's a talent in that as well as in the longer review. Pith. Succinctness. But Pulitzer Prize committees don't see things that way. Hence, less acclaim for Mr. Siskel's writing.

Dashiell Hammett wrote in a terse style and never won the Nobel Prize for literature either, but was vastly influential on all kinds of writers who followed, and not just in the detective vein either.

ROGER TALKED HIS WAY INTO A FANDOM...SISKEL WAS ABRUPT AND HARDER TO LIKE.

He didn't publish as many books, and he didn't live as long. Less exposure.

Gene didn't have Oprah backing him.

Seriously a number of factors , many were listed above.

I think Siskel represented what the typical film snob was in the public eye, whereas Ebert was much better at self-marketing and being relatable. Ebert just always seemed more approachable. Siskel was kinda like the film version of Simon Cowell.