I'm grateful for this thread, as I had been struggling with my own personal evaluation system for restaurants.
I've established a number of evaluations, outlined as follows:
1. X/5 - The value of X represents my own personal position of the place. For me, food is the pinnacle factor. As long as all other factors are acceptable/average or better, X will remain solely based on food related metrics. One could focus on any factor or mix of factors when determining their X-evaluation, and the denominator is negligible.
2. RANK - This is a personal/emotional evaluation which determines the hierarchy of best to least best. RANK is essentially the filtered results of "X/5". This is where the non-food related metrics come into play, in addition to identifying which place had marginally better food than another. For me, this is where 'overall experience' has the greatest impact. The evaluation is more personal/emotional, as opposed to technical/logical as in the following evaluation.
3. RATING - This is a technical/logical evaluation, and is the most difficult to conclude. It attempts to remove bias and provide a comprehensive rating. Consistency should always be used to balance all metrics, especially in this evaluation. For me (in order to rate a restaurant) I must have either tried a minimum of five courses, or made more than one visit. Establish all the categories/metrics that you personally value, and assign weighting to each. For me those include FLAVOR 45%, CREATIVITY 15%, PLATING 15%, SERVICE 10%, AMBIENCE 10%, and ACCOLADES 5%. Use your chosen denominator and rate each category/metric, then multiply & divide accordingly to get the rating. It's fun to compare these results with your personal/emotional ranked hierarchy.
I also have a system in place to guide me towards bucket list destinations. This is mainly associated with fine dining establishments. I use LaListe (which for those who are unaware, uses an algorithm of all credible sources in order to arrive at the world's greatest 1000 restaurants) and then I re-combine it with Michelin, S.P., and the trained palates of Andy Hayler and the folks at OAD.
Another consideration is the theory of relativity, or the law of diminishing returns. For example, if you're blown away by your first ever gourmet experience and always hold the establishment high on your list, you may want to re-visit after experiencing many other incredible places. You may find that it relatively less impactful at that point... or in other words, the return will be diminished.
Finally, I personally find it important to establish a benchmark - a benchmark which doesn't care about what a place is trying to achieve; doesn't care about the genre of food; doesn't care about cost... Ask yourself "what is my definition 100% perfection". In this situation, you CAN compare apples to oranges to bananas, because the question becomes "which flavor blows me away the most" and "which experience brings me the most pleasure" etc. In rating a restaurant, one should be perceptive enough to distinguish the relative importance of the gastronomical aspect vs. everything else...
YOU ARE THE CRITIC.