In other words, when reviewing a manuscript for a journal, should the depth of the critique be proportionate with the impact or reputation of the journal?
1. That a journal is "reputed" does not refer to the journal being good - it only says that it has a reputation. Very many here make that mistake in interpretation. Remember that.
Here is the definition from the Cambridge dictionary:
"Said to be the true situation although this is not known to be certain and may not be likely". So there you go. If you want to refer to something actually being good, the word "reputed" should not be used.
2. The best potential reviewers will likely turn the offer down, as being a very good reviewer typically also means that they are excellent scientists, who most likely will not accept the "offer" to be a reviewer - they are too busy!
3. The answer to the original question is: "Definitely NOT". And who are "the best reviewers" anyway? Do you know? Every manuscript shall be treated with exactly the same scrutiny - otherwise the system is either corrupt, or it is in a shambles. Who are the best reviewers anyway? They may not be the ones who are the most respected scholars, in fact.
Maybe they do in some cases, Mohammad, but the very best potential reviewers will most likely turn the offer down, as they have too many better things to do - according to them, at least.