I'm not trying I convince you b/c you can be entitled to your opinion but at least establish an unbiased criteria to judge the fighters. If you hold finishing ability higher, cool. But a loss is a loss no matter the way or where it took place. GSP had only been fighting for two years when he fought Hughes and 5 when he fought Serra, that is relatively young. Anderson was in his 9th year before he fought for the UFC title, his experience before joining the UFC was two times what GSP's was. GSP actually has the better record, been finished the same amount of times, and is younger, probably just hitting his prime.
The reason I typed all that was simply to illustrate where they were at the same time in their careers and to show GSP has many more years in his prime and could possibly surpass Anderson in ways of accomplishments. I'm not saying he is a better champion or the better fighter now but I will argue regardless of his finishing percentage and a 5 year old loss, GSP is already comparable.