Note: GT is exluded from this history, events beyond Majin Buu have become an alternate timeline.

It is a decade since the world has been cleansed of the evil that was Majin Buu, the 37th Tenkaichi Budokai is about to be held. Goku and the others enter, and Goku reveals why they have come there: Goku claims that Majin Buu has been reincarnated into a pure human body, with his power intact, but none of his evil. Of course that boy was Uub, and it soon becomes apparent that what Goku claims is true, because Uub can keep up with Goku like no other Human would be capable of. Also Pan was there, but neither are relevant. Long story short, Goku goes into seclusion with only Uub to begin maximizing his power. Beyond this point is where the alternate timeline begins.

Also I want to mention their ages as according to this timeline. The ages listed below are how old they are a decade after Buu, and these are their physical ages, not actual ages, because Goku's physical age for instance is much lower than his actual age because he has been Dead for long periods of time.
Vegeta: 50
Tien: 48
Yamcha: 48
Krillan: 45
Goku: 38
Gohan: 28

A decade later:
Everything is going peacefully. Pan and Uub are grown up. All the original z-fighters except Gohan are old as hell, even Gohan has been in decline for years because of his Halfie DNA. The only original z-fighter that has even successfully maintained their top power is Goku due to his constant effort. The only major people in this era are Goku, Uub, and Pan, the others are too declined to really be in the same league as them. Gohan may be in a close second in power though, even though he is far declined he still has the power of a Super Saiyan 2 Mystic at his disposal

Another decade later...
I just thought this decade was relevant because at this point not even Goku could maintain the power he once had, and by this point Pan and Uub are the only major people in terms of power. But, even though its 20 years after Buu, there has been no earth-threatening events. Also its not far from this time, that Vegeta dies, just so you know.

Not many years later there is a massive explosion that destroys the north quadrant of the galaxy completely. This explosion is not caused by a person, but is more similar to the supposed "big bang" that started the universe as scientists know it today, except on a smaller galactic scale. Unknown to anyone though, the trigger for this this was an instability between two dimensions, which was actually caused by Majin Buu when he somehow used his power to open a dimensional portal between the room of spirit and time and kami's tower, this caused a irrepairable break in spacetime which began to expand in the room of spirit and time, until it reached critical mass and became a singularity in both dimensions, destroying the north quadrant of the galaxy, but also destroying an equally large chunk of the supposedly infinite space inside the room of time. It looks like Majin Buu did win in a way, in the long run.

The singularity of course took the form of a super-massive black hole in the north quadrant, which had the gravitational pull of hundreds of thousands of billions of suns and began to affect the other quadrants of the galaxy. A resident of one of the remaining quadrants who had the knowledge solved this problem before it was too late, it is unknown exactly -how- they restored the damage, but it seems like a similar method to the Dragon Balls, except whatever method they used it was thousands of times more powerful than the Dragon Balls. Thanks to these people the North Quadrant was somehow restored, and the black hole somehow disappeared. All planets that had -ever- existed in the north part of the galaxy were restored to their places, but only a fraction of the life on each one was restored. None of the z-fighters were restored to life from this action, only children, children so young they retained no memory of the past.

It is now a century after Buu was defeated. Nobody has any memory or relation to the former earth or any other planet for that matter. There are only ruins from that era, and vague clues, but that is all.

Other notable events:
Ten years after the defeat of Cell a probe reaches earth from deep space, and mysteriously knows exactly where to find Gero's lab, which was destroyed years earlier. It makes it's way to the fragments of Gero's computer, analyzes them, and sends what data it can back to wherever it came from. It turns out that it came from the Android Planet, which was another incomplete project of Dr Gero, and was programmed to take his operations to deep space in the case of his death and that Earth was somehow compromised. The Android Planet was far from a planet when Gero first created it, it was a small space lab with a sentient computer which controlled millions of nano-robots. The space lab then began advancing itself to the point that it became so large and sophisticated that it became a small planet, and began creating more sentient Androids to populate itself. Ten more years later the probe returns, with data on Gero's most perfect creation, Cell. Unfortunately, the data is incomplete, the Android Computer fills in the gaps as best as it can but even though it was programmed with the knowledge of Gero, it is still not as innovative or as good as improvising. It is a far harder and longer process to create a Bio-Android than it is for regular Androids, so the Android Planet does not construct them very often. It would take the Android Planet 80 more years before it had become capable of making a working Bio-Android, bringing us to present day (Year 0).

It has been 100 years since Majin Buu was seemingly defeated. And it's true, that Majin Buu is truly dead. But not all of him is gone...It seems that Goku's Genki Dama did not truly erase all of Buu's body from existance, it just broke him down into such small particles that he was incapable of restoring himself as he once was. That Majin Buu is dead, but those individual particles, have been slowly regenerating all over Kaioshin planet for 100 years now, and finally they have reached a point where they are coming back to life in the form of Majin Buu-like creatures that still have a portion of his power, but are seperate beings and slightly mutated from the original. Looks like Majin Buu's threat has returned, and this time it's not just one Majin the universe has to deal with.