Pirkei Avot - Ethics of the Fathers

~Level 1~
Bartenura - "one with whom people are pleased, G-d is pleased with him" - whoever is beloved below, then it is known that he is beloved above.

~Level 1~
Tosfot Yom Tov - "G-d is pleased with him" - as written: "But the mercy of the L-ord is from everlasting to everlasting upon them that fear him" (Tehilim 103:17). Namely, that whoever has a "string of kindliness" drawn after him, it is known that he has fear of Heaven..

~Level 1~
Tiferet Yisrael - "one with whom people are pleased" - he also observes the duties towards other people to do good to them and all the more so to not do bad to them. Through this, they are pleased with him and they will love him.

"G-d is pleased" - the Holy One, blessed be He, loves him.

"but one from whom people are displeased" - he does not guard his obligations towards them, even though he keeps the commandments between man and G-d and learns torah.

~Level 2~
Tiferet Yisrael - "G-d is displeased with him" - as we learned: (Yomah 86a):

" 'And you shall love the L-ord your G-d' (Deut.6:5), i.e., that the Name of Heaven be beloved because of you. if someone studies Scripture and Mishnah, and attends on the disciples of the wise, is honest in business, and speaks pleasantly to others, what do people then say concerning him? 'Fortunate is the father who taught him Torah, fortunate is the teacher who taught him Torah; woe unto people who have not studied the Torah; for this man has studied the Torah look how fine his ways are, how righteous his deeds! Of him does Scripture say: 'And He (G-d) said unto me: you are My servant, Israel, in, whom I will be glorified'. But if someone studies Scripture and Mishnah, attends on the disciples of the wise, but is dishonest in business, and discourteous in his relations with people, what do people say about him? 'Woe unto him who studied the Torah, woe unto his father who taught him Torah; woe unto his teacher who taught him Torah!' This man studied the Torah: Look, how corrupt are his deeds, how ugly his ways; of him Scripture says: 'In that men said of them: These are the people of the L-rd, who have been expelled from His land'"

~Level 3~
Rabbi Avraham Azoulai - Ahava b'Taanugim - some explain "one with whom people are pleased..", that people say: "praiseworthy is he who bore such a person..", then "G-d is pleased with him". For the torah is praised through him and the Name of Heaven is sanctified through him.

Some explain "one with whom people are pleased..", i.e. they have contentment in Olam Haba (the afterlife) due to him because he brought merit to them, then "G-d is pleased with him..".

And "but one from whom people are displeased.." - that is to say: one who says: "peace be unto my soul. I and my family will serve G-d. But what do I need to guide and bring merit to others for"? And no creature ever received merit due to him, i.e. he never brought contentment (nachat Ruach) to G-d. For G-d desires only in he who brings merit to others...

Some explain: since there are commandments between man and G-d and also commandments between man and his fellow man. And in order that one not think to say that the Holy One, blessed be He, desires more in one who fulfills the commandments between man and G-d.. [Thus, "one with whom people are pleased, G-d is pleased..."]

Alternatively, one who is whole in fulfilling the commandments between man and his fellow man, all the more so will he fulfill the commandments between man and G-d. For it is more difficult for a man to do the will of each person, since each person's will is different.

~Level 3~
Avot d'Rebbi Eliezer - "ruach habriot nocha mimenu" - he did not say "people are pleased from him" (nochim, i.e. plural tense). But rather "people are pleased (nocha, i.e. singular tense) from him". (for it hints not to people but to the ruach - the spirit)

For in truth, a man can be pleasing to others but not pleasing to G-d. Thus, the mishna specifically writes "ruach (the spirit)" of others. The "ruach" is the Neshama (soul), as written: "and the ruach will return to G-d" (Kohelet 12:7). This is the intent of the mishna in saying "the ruach of others is pleased from him". Namely, one who teaches torah to his fellow, or some good trait, or good deed - ruach haMakom (G-d) is pleased with him.
Every person can fulfill this. For example to advise his fellow not to do something which is against the advice of the torah.

~Level 4~
Chachma U'Mussar chelek beit, 110 - "people are pleased" - in the Sefer Chasidim (siman 224): " 'He fulfills the word of His servant, and the advice of His angels He fulfills' (Isaiah 44:26) - the upper ones accept the view of the lower ones (elyonim maskimim l'daat tachtonim) (the upper ones. When the upper ones say: 'these people deserve such and such a punishment or reward, the Holy One, blessed be He says: 'wait until the tzadikim say thus'. Hence, the Holy One, blessed be He, did not say a teaching of R.Meir (since he learned from Acher) until an Amorah (talmudic sage) said: 'R.Meir found a pomegranate. He ate the fruit and discarded the peel' (i.e. he took the good and discarded the bad from Acher). Then G-d said: 'My son Meir said..' (i.e. G-d began to say the teachings of R.Meir). For He wanted the upper ones and lower ones to agree on His trait of justice." end quote.

This is a wonder. For after the torah was given to the sages of the yeshiva below, as written: "it is not in the Heaven" (Devarim 30:12), and the opinion was given to them, thus perforce all the time the sages of the generation do not accept a person's torah, deeds, and conduct, it will likewise not be accepted in Heaven, even if the person is right, until his words have been clarified to the sages of the yeshiva below.

With this we will explain our mishna. When is "G-d pleased with him"? When the people begin to be pleased with him, here below. But all the while this is not the case, then even if above, it is known that his conduct is praiseworthy, but nevertheless "G-d is not pleased with him". For the knowledge is given to the great sages of the generation, and as they judge here in this world so too thus it will be accepted above.

According to this, a man must examine whether his torah and deeds are according to the depths of the true halacha to fulfill his obligation to above and afterwards, he also needs to clarify whether the understanding sages [below] also approve of his torah, deeds and conduct. For without this, it will not be accepted above. This is the meaning of "you shall be clean of G-d and Israel" (Bamidbar 32:22)...