Is Bakuman based on the life story of the author himself/the people he knew or is it a manga with a fictional story?
Ashirogi Muto appear to be based on Tsugumi Ohba and Takeshi Obata.
Akito Takagi and Moritaka Mashiro resemble Ohba Tsugumi and Obata Takeshi, respectively. The writer and the artist part being analogous to Ohba being the writer and Obata being the artist, Mashiro's semi realistic style being akin to Obata's, the darker themed manga that get better reception (which was true for Ohba whose most sold manga is Death Note) and even Takagi's failed attempt at action manga resembles Obata's failure, Rampou, that got cancelled after the second volume. Takagi, according to Bakuman, is best at writing dark and elaborate stories; this could be parallel to Ohba's way of writing as an author (for example, Death Note). There were also chapters that talked about serious humor in Bakuman; this "serious humor" can also seen in Death Note.
Also notable is this statement made by a user of the forum link:
At the end of every chapter there's a page that shows a Name made by Ohba (with funny and ugly drawings just like the ones that Tagaki used to do) and a Name made by Obata, with better pannels and drawings (just like the ones that Mashiro makes)
It's speculated that Niizuma Eiji is based on Eiichiro Oda and Tite Kubo.
Niizuma Eiji seems to based on Oda, with all the encompassing success of their manga and the rather childlike purity of their love of the artform.
The editors of Bakuman appear to be based on real-life editors.
Ashirogi Muto's editor, Hattori Akira, is based on two real life editors. The name is based on Hattori John Batist Akira while the likeness is based on Saito Yuu. Aida Souichi, team leader of Hattori in Bakuman, is based on real life current vice editor-in-chief Aida Souichi. He was the editor for Bakuman from Chapter 1 till around Chapter 91. They basically used the same names (even the Kanji are the same) as the real life editors for most of the established editors.
Hiramaru's comic tendencies with animals, exasperation at his editor, and laziness draw a parallel to Sorachi Hideaki, mangaka of Gintama.
He may also be based on Yoshihiro Togashi who is just as lazy and also has a mangaka wife: Naoko Takeuchi, the mangaka of Sailor Moon.
Nobuhiro could be compared to Hiroshi Gamo, a real-life mangaka famous for his gag manga and speculated to be Tsugumi Ohba.
Aoki's specialization in romance manga, along with her experience and popularity with the series, draw a parallel to Kawashita Mizuki, mangaka of Ichigo 100%, Hatsukoi Limited, and Ane Doki.