Delillo I've read: Americana, End Zone, Great Jones Street, Ratner's Star, Players, The Names, White Noise, Libra, Mao II, Underworld, and Cosmopolis. (I think that's it.) I've also read Delillo's somewhat famous essay on 9/11 as well as a short story or two.
Bellow I've read: Seize the Day, Herzog, Mr. Sammler's Planet, The Dean's December, Ravelstein, and perhaps a short story or two. A short piece by Bellow I like is his introduction to Allan Bloom's The Closing of the American Mind, where, to me, he makes it clear that he does not necessarily see things the same way. I'm not sure that the university is still a place where people with even strongly opposing political views might support each other's work or at least respect its place in print. (Well, I guess these days everyone is too busy with their teaching overloads, publication schedules, and "specializations" to read each other's work. And that would more likely be online, yes, indeed.)
OK. In conclusion, I've read more Delillo than Bellow (and I'm willing to wager that you have too) although Bellow would seem to be a more significant influence in my own literary efforts, if either of these guys is any kind of influence at all. (Well, I guess you can't have an alienated male protagonist or antihero in an American novel without implicitly referencing these two.) I've tried to describe Fight for Your Long Day as a cross between novels by Saul Bellow and Dan Fante, but I'm not sure it would be understood that way, and I doubt many of my readers will have read much by those two anyway. (This does not imply I have "many readers" as of this blogging.) I'd probably be better off comparing it to movies. . . ah, humanity.
As an aside on Italian American novelists, I should note that for me, Don Delillo completely kicks Richard Russo's ass and is the undisputed lone heavyweight in the category although Dan and John Fante would be my sentimental favorites on this list and I'm pulling for Dan Fante's buddy Mark SaFranko (who was kind enough to let me know soon after this post that in fact he is not Italian; okay, we'll handle that another time but keep his name under the bright lights of USK) as well as two of the guys Dan Cafaro has signed up for publication at Atticus Books. Maybe we'll Jew-list another day. Oy vey.
(Mark's correction just reminded me of a thought I had on the way to the library. Saul Bellow was born in Quebec.)