The IBM PC came with Basic in ROM as well as the ability to load and save programs to tape. It was also available with color graphics.
...Of course most were sold with monochrome graphics and the clones cut out the built in Basic because it was IBM's code, as well as the tape routines, because floppies were so prevalent.
80 column support was key. More or less CP/M compatibility was also key.
One thing the 8088 PC had compared with the 8-bits was rudimentary memory management in the form of the segment registers. This decoupled the OS and BIOS from application code in a way that was not possible on previous 8-bits. People forget that in the world before memory management that if you wanted to change the OS your only option was to do something like "sysgen" a horrible slow process where you re-linked the OS and all application code. IBM's OS 360 and DEC's RSX-11 had this concept.
People hated segment registers, but the only other alternative was position independent code, like on the 6809. I would argue that this is worse, because it slows execution time.
...Of course most were sold with monochrome graphics and the clones cut out the built in Basic because it was IBM's code, as well as the tape routines, because floppies were so prevalent.