You are wrong because there is no objective scale for "best".

Some individual categories might have such a scale (for example, graphical resolution), but judging strictly by technical, measurable standards would not yield FFX as the "best" in almost any category, and certainly not overall.

Getting past technical standpoints, we reach the quasi-quantifiable issues. Things like "most mini games" are measurable, but fail to take into account quality, not to mention varying definitions of the terms used.

Then there is the question of how far down to break major categories. For example "best art design" can be split into "best monster design", "best world design", and "best character design". But each of these can be further subdivided, as well as each being weighed differently by each individual judge. Objectively, each category would have to be weighed either equally, or proportionately to screen time, while to many judges, a particular aspect may be far more important.

And then, of course, there are the majority of unquantifiable aspects of the game. There is no objective measure for aesthetics (not simply visual, but of any type). Beauty is in the eye of the beholder. Some people love Khimari's design, some hate it, some just don't care one way or the other. Some people love the world design, others don't. Characterization, lore, music, customization, gameplay, even the structure of levels, none of these things can be objectively measured.

With the majority of the game (and, to most people, the most important parts of the game) being subjective, your assertion falls apart. And if you ignore the subjective parts and focus on what can be judged objectively, FFX is not likely to come out on top, even if you could find an objective way to weight all the various issues at hand.

Is FFX a great game? Sure. Is it the best FF game? Possibly. Certainly to some people. Is it objectively the best? No.