There are different Greek words that are all translated to the same English word "serve" in our modern English bibles:

For example, in the same ESV translation Jesus said:

The Son of Man came not to be served but to serve” -- Matthew 20:28 (ESV)

but then Jesus also said:

“If anyone serves me, he must follow me; and where I am, there will my servant be also. If anyone serves me, the Father will honor him.” -- John 12:26 (ESV)

Jesus did not contradict himself. This is a result of confusing translations.

Worship service

The following scriptures use the Greek word "latreuó":

“Blessed be the Lord God of Israel... serve (latreuó) Him without fear, in holiness and righteousness before Him all our days. -- Luke 1:68,74-75 (ESV)

There was a prophetess, Anna, the daughter of Phanuel, of the tribe of Asher... She did not depart from the temple, worshiping (latreuó) with fasting and prayer night and day. -- Luke 2:37 (ESV)

God spake on this wise, That his seed should sojourn in a strange land; and that they should bring them into bondage (douleuó), and entreat them evil four hundred years. And the nation to whom they shall be in bondage (douleuó) will I judge, said God: and after that shall they come forth, and serve (latreuó) me in this place. -- Acts 7:6-7 (KJV)

Paul replied... "But this I confess to you, that according to the way, which they call a sect, I worship (latreuó) the God of our fathers, believing everything laid down by the Law and written in the Prophets. -- Acts 24:14 (ESV)

Then Paul stretched out his hand and made his defense... now I stand here on trial because of my hope in the promise made by God to our fathers, to which our twelve tribes hope to attain, as they earnestly worship (latreuó) night and day. -- Acts 26:1,6-7 (ESV)

Paul stood up among them and said... this very night there stood before me an angel of the God to whom I belong and whom I worship (latreuó) ... -- Acts 27:23 (ESV)

God is my witness, whom I serve (latreuó) with my spirit in the gospel of his Son... -- Romans 1:9 (ESV)

We are the circumcision, who worship (latreuó) by the Spirit of God... -- Philippians 3:3 (ESV)

I thank God whom I serve (latreuó), as did my ancestors, with a clear conscience, as I remember you constantly in my prayers night and day. -- 2 Timothy 1:3 (ESV)

Therefore they are before the throne of God, and serve (latreuó) Him day and night in His temple. -- Revelation 7:15 (ESV)

No longer will there be anything accursed, but the throne of God and of the Lamb will be in it, and His servants will worship (latreuó) Him. --Revelation 22:3 (ESV)

"latreuó" is always used in connection to worship God and never as a form of worship service to Jesus. Jesus was worshipped differently, because this kind of worship service is forbidden to anyone other than God Himself:

Jesus said to him, “Be gone, Satan! For it is written, ‘You shall worship the Lord your God and Him only shall you serve (latreuó).’” -- Matthew 4:9-10 (ESV)

Jesus answered him, “It is written, “‘You shall worship the Lord your God, and Him only shall you serve (latreuó).’” -- Luke 4:8 (ESV)

Therefore God gave them up in the lusts of their hearts to impurity, to the dishonoring of their bodies among themselves, because they exchanged the truth about God for a lie and worshiped and served (latreuó) the creature rather than the Creator, Who is blessed forever! -- Romans 1:25 (ESV)

General minister service

Then he will say to those on his left, "Depart from me, you cursed, into the eternal fire prepared for the devil and his angels. For I was hungry and you gave me no food, I was thirsty and you gave me no drink, I was a stranger and you did not welcome me, naked and you did not clothe me, sick and in prison and you did not visit me."
Then they also will answer, saying, "Lord, when did we see you hungry or thirsty or a stranger or naked or sick or in prison, and did not minister (diakoneó) to you?"
Then he will answer them, saying, "Truly, I say to you, as you did not do it to one of the least of these, you did not do it to me." -- Matthew 25:41-45 (ESV)

Jesus was not requesting prayer, worship or sacrifice, but ministry service.

“If anyone serves (diakoneó) me, he must follow me; and where I am, there will my servant be also. If anyone serves (diakoneó) me, the Father will honor him.” -- John 12:26 (ESV)

Another example where Jesus was "served":

Then the devil left him, and behold, angels came and were ministering (diakoneó) to him (Jesus). -- Matthew 4:11 (ESV)

The angels did not worship Jesus, instead they attended to his needs so that he could survive in the desert.

Now as they went on their way, Jesus entered a village. And a woman named Martha welcomed him into her house. And she had a sister called Mary, who sat at the Lord's feet and listened to his teaching. But Martha was distracted with much serving (diakoneó). And she went up to him and said, “Lord, do you not care that my sister has left me to serve (diakoneó) alone? Tell her then to help me.” -- Luke 10:38 (ESV)

Simon's wife's mother lay sick of a fever, and anon they tell him of her. And he came and took her by the hand, and lifted her up; and immediately the fever left her, and she ministered (diakoneó) unto them. -- Mark 1:30-31 (KJV)

And the twelve summoned the full number of the disciples and said, “It is not right that we should give up preaching the word of God to serve (diakoneó) tables.” -- Acts 6:2 (ESV)

So he sent into Macedonia two of them that ministered (diakoneó) unto him, Timotheus and Erastus; but he himself stayed in Asia for a season. -- Acts 19:22 (KJV)

At present, however, I am going to Jerusalem bringing aid (diakoneó) to the saints. -- Romans 15:25 (ESV)

Obedient bondage service

Now his older son was in the field, and as he came and drew near to the house, he heard music and dancing. And he called one of the servants and asked what these things meant.

And he said to him, "Your brother has come, and your father has killed the fattened calf, because he has received him back safe and sound."

But he was angry and refused to go in.

His father came out and entreated him, but he answered his father, "Look, these many years I have served (douleuó) you, and I never disobeyed your command, yet you never gave me a young goat, that I might celebrate with my friends."

-- Luke 15:25-29 (ESV)

They answered him, “We are offspring of Abraham and have never been enslaved (douleuó) to anyone. How is it that you say, ‘You will become free’?” -- John 8:33 (ESV)

No one can serve (douleuó) two masters, for either he will hate the one and love the other, or he will be devoted to the one and despise the other. You cannot serve (douleuó) God and money. -- Matthew 6:24 (ESV)