I'm strictly going off of what I see in the films, I'm not familiar with the extended universe lore. They say he'll bring balance to the force.
uhhh, okay? what balance?
at the beginning of Phantom Menace it's pretty clear that there isn't much of a rift in the force. As Mace Windu points out, the Sith had not been seen for over a millenium. Now before you go into the presence of Darth Sidious and Maul:
yes, they're sith in hiding, and their about to expose themselves. that being said, had Anakin not gotten involved Sidious probably would've had a few problems to deal with. The entire Jedi order would've eventually figured out what was going on. Maul was killed, and still probablyh woudl've been killed, Dooku would've been killed as well, and Sidious would eventually be jumped by entire order. It was because of Anakin that Sidious survived his encounter with Windu.
Furthermore, What balance are they talking about? Qui-Gon assumes Anakin is the chosen one BEFORE he senses Darth Maul. this would imply that there's some other issue going on in the force that the movies never bothered to point out.
What about the separatists? what about them? they're nothing, the Jedi can dispose of them like nothing, they don't need Anakin for that.
as much as I like Qui-Gon, it's pretty apparent that he's an idiot. He's basically responsible for harboring the ambitions of one of the galaxy's most feared Siths alliances. Had he just freed Anakin, and then scramed without him the war may not have started, or at least not escelated to its ultimately conclusion.