There always some other reference that is at times better than what you found. That is part of research. Literature review helps you find the most recent but it does not mean its the most relevant or even the best. Something old can be better, more relevant and best. Many old things and especially people are dearest to us.
It is more likely that what is published first is the more recent, but sometimes publishers and other businesses are getting to be first in a search, for payment. That is , they buy their way to be the first in a search retrieval.
It does never mean to be the best. Even if some say that it is the best then there are surely others who think and perceive other books to be the best. Its kind of relative. Quantities never mean quality all the time but it does mean to be worthwhile to pay attention to it as that may be accepted but not necessarily. There is always some possibility for sudden change of the thought to be the best.
By default the most cited ones usually appears on the first page of your search. However, there is an options where you can sort the appearance by date as well. Other databases do have quite a few sorting options unlike google scholar.
2) Appearing first on the page does mean that the Google displays or throw the content "relevant" to the key word/meta tag /topic name that one is searching for in the web, but does not mean it's the best.
3) Some times, Google displays the content based on premium services like Search Engine Optimization (SEO) service. In any case, it works on relevancy but not quality.
4) Unless there is something which shows the number of reads or the number of views of that particular content, one can't say or claim it's the best.
There always some other reference that is at times better than what you found. That is part of research. Literature review helps you find the most recent but it does not mean its the most relevant or even the best. Something old can be better, more relevant and best. Many old things and especially people are dearest to us.