That sounds exactly like what a "UFC only" would say. uhuh
In all seriousness though, UFC has become the most important organization recently; however, it is not the only one that matters.
Even now, there are fighters from other organizations that many believe are actually better than some current UFC champions. There's even more non-UFC fighters that are considered top tiers. For a recent example, look at Carlos Condit. Many people have Dan Hardy ranked around #4 WW, but Carlos completely laid Dan the **** out.
Many fighters refuse to join UFC due to Dana's desire to completely own all aspects of his fighters, and even UFC fighters have expressed discontent with Dana. It sucks, but there are great inter-organizational fights that we will probably never see.