And i would've have gotten away with it too if it werent for those meddeling kids

[Forsaken Lover]

Well, as SE itself said, Ultimecia was only effecting the planet.
So, she absorbed all the time and existence of the planet and then after that, nothing is left alive except her.

[Sarc the Swordsman]

Queen Brahne!

If Kuja hadn't intervened, or perhaps had been killed by Bahamut; she probably would have succeeded in conquering the whole world. Alexandria wouldn't have been destroyed; and would have been the most powerful country.

She succeeded in getting rid of a lot of things that stood in her way, anyway. Burmecia, Cleyra and even Lindblum to an extent.

[The Crystal]

It would have been interesting to see what, exactly, Ultimecia would have done if she defeated SeeD. It's like, okay, you're safe... now what?

She would continue to absorb all existence(like she was doing during the final battle), until it's over.

Then she would probably use her godlike power to recreate everything in her own image. Because I don't believe she would just sit there in the void doing nothing for the rest of her existence.

This is why I think it would be awesome if she won. Can you imagine all existence being created(or recreated in this case)?
It would be something amazing to see.