The major point that you appear to be missing is who decides what is the "best"? By what measure is it the best? Is that voted on by your peers? An independent panel judging? Is there some other metric that indicates yours is better than others? Or is it the best because you say it is?
Unfortunately it appears to be the latter, which unfortunately completely nullifies your assertion that you have integrity and are trustworthy.
Now, if you were to say your forum is the biggest, or the busiest or the most popular then this is measurable and, as long as it is true, you'd be well within your rights to boast about that as much as you like and no one would be able to disagree. However, saying something is "the best" is completely subjective unless it can be objectively measured by something specific.
At the moment your arbitrary and baseless claim that you are the best is just going to do you more harm than good.