Does the prayer of one who feels envy or jealousy because of the devotion of another worshipper next to him become invalid?

Prayer is not invalidated merely by feeling envy or jealousy. Rather, one should strive for khushu' (devotional concentration) in it. The forbidden envy (hasad) is the wish for a blessing to be removed from another, based on the Prophet's (peace be upon him) saying, "Do not envy one another," and Allah Almighty's saying, "Or do they envy people for what Allah has given them of His bounty?" (Quran 4:54). As for ghibtah (emulation), which is wishing to attain a blessing without wishing for its removal from another, there is no harm in it.