Not much of a topic, but I'll bite.
I believe if you do a little research you'll find that (or at the very least it is theorized that) Toriyama intended to replace Goku with Goten after Cell exploded and killed him. Goku was too popular though, so ultimately he was brought back. That said, Goku isn't necessarily always the "star" of the show. There were several gaps where Goku was barely seen, most notably when he was dead and Gohan became the focus, though in fairness as soon as Buu showed up Goku came back. Gohan didn't have a major enemy to fight.
Some sort of off-shoot focusing on Vegeta would be cool, maybe a short series focusing on his time working for Frieza. I can think of a few ways they could make that interesting. Making him the main character of the main series though? That just doesn't work. He's a darker counterpart to the main character, and in a lot of ways he's there to balance the main character out, not replace him.
Oh, and there were only a few occasions when Goku and Vegeta were more or less equal in power, and each time Goku soon jumped ahead again. That was kind of the whole point.
I think Vegeta is way more interesting a character, but I think good guys across pretty much every medium are written to be way less interesting than the bad guys are. Vegeta gets a good amount of screen time though so I'm happy with his role. A re-imagining based on his point of view would be cool though.
Vegeta isn't dark. He's really not any less one dimensional than Goku is. Well he is, but that doesn't say much. "Oh mwahahaha I'm a bad guy and I want to conquer earth! Oh, now I'm not and I'm still a dillhole even though I'm a good guy and don't want to admit it! OK, now I'm good and I'll admit it... But I'm still a jerk!" Vegeta is a very light character if you think about him. His arrogance adds to the comic relief of the series and that's why he's so easy to make fun of. Alternate Reality Dragon Ball Z understood that. That's just my opinion.
@DBZ_universe come and weigh in on this topic