Cena's accomplishments in the developmental territories is ABSOLUTELY Relevant to this debate. The sheer fact that you dismiss them shows you may not understand the industry at all.
Now lets move on to your list of guys:
Shawn Michaels - Entered the WWE as a tag team specialist with Marty Jannety as The Rockers based on their accomplishments in the AWA. It wasn't for a couple of years that he was made a singles wrestler.
Steve Austin - Entered the WWE as the Ringmaster with The Million Dollar Man as his mouthpiece, thus negating his mic skills
Edge - Another tag team specialist, ala Shawn Michaels
JBL - Never had a workable angle to use before he was made to tag with then Faarooq which became an angle for years to come.
These guys don't have total control of their angles or storylines so to say certain guys "pay their dues" on the active roster is a bit ridiculous. All these guys either did it in developmental territories or other brands before coming to the WWE. Obviously Cena gets a push due to his mic skills plus the fact that his character can instantly draw pops and/or heat at any given time.