[gorthaur_cruel]

No way. The only person who would really have a chance would be Gandalf and even his chances wouldn't be anywhere close to 99%.

I'm assuming you're talking about Tolkien's letter where it said only Gandalf would have a chance of beating Sauron. But if you re-read it, it actually says only Gandalf had a chance of defeating Sauron 1v1 with the Ring. Elrond and Galadriel could wield the One Ring to build up armies and defeat Sauron. Here's the quote:

In any case Elrond or Galadriel would have proceeded in the policy now adopted by Sauron: they would have built up an empire with great and absolutely subservient generals and armies and engines of war, until they could challenge Sauron and destroy him by force. Confrontation of Sauron alone, unaided, self to self, was not contemplated.

However, the chances of successfully overthrowing Sauron using the Ring still would be higher than the chances of destroying the Ring, so I agree that Boromir's actions were understandable.

I've been sitting here thinking for a while and I'm fairly certain that if I would've been in Boromir's position (I hate to say this) I probably would've tried to take the Ring like he did.

My point exactly.

The problem with this statements is that Sauron never could be truly defeated as long as the Ring existed. He could come back in another couple thousand years, and then you are back where you started. The point of destroying the Ring was (I'm paraphrasing) to take care of the problem once and for all, not just for one age of men.

Really? Tolkien says that if Gandalf mastered the Ring and defeated Sauron, then...

If Gandalf proved the victor, the result would have been for Sauron the same as the destruction of the Ring; for him it would have been destroyed, taken from him for ever. But the Ring and all its works would have endured. It would have been the master in the end.

The difference with that case and Isildur's case is that the Ring did not adopt Isildur as his new master. Isildur never mastered the Ring's powers. If somebody else masters the Ring, Sauron loses his mastery over it. But the Ring would then eventually master the one who mastered it. I think I said enough "master"s now.
Also, if there was a 99~100% chance of failing to defeating Sauron once and for all, wouldn't it be better to take the high chance of defeating Sauron for now?

Isildur was strong.

I know...I was just saying what Boromir thought. But even then, you see, Isildur wasn't corrupted by the time he died, so we don't know how long he'd have held out. The effect of not wanting to lose the Ring is only the signs of corruption, not corruption itself. He never tried to do any evil before he died.