“You end up with the person entity that you worship after you die, so the difference is in ultimate attainment.”
God is eternal, whereas a person dies.
The basic difference is evident in the example of Gopis who loved and worshipped Krishna versus any woman who loves and worships her husband/or another person.
Gopis who loved Krishna, as their paramour became lust less, desire-less, and they lost their bodily consciousness and automatically gained profound knowledge of soul and spirituality alike, and they gained the ultimate redemption and are forever remembered and revered in the spiritual world.
Let us take an example of a woman who loves her husband who is not a God, her desires increase day by day which her husband gets tired of fulfilling, her lust also increases day by day, but since she becomes old and her body does not keep up with her desire she then stops sexual activities, it is not because she has become lustless. The association with the body and bodily keeps on strengthening with time, and at the end of their life they die to regret all their bodily relation because they are of no use after death. And they are subjected to the cycle of birth and death after their death. So no ultimate redemption!
Worshipping an alive person usually comes from one’s desire to become God and have an unquestioned sensual indulgence, people like these go to hell forever I guess.
So, the difference in worshipping God and other person is as much as the difference is between getting married to a true noble King versus a corrupt poor man. Your life, your afterlife and what you gain, your spiritual and social status, your internal peace and satisfaction all things are jeopardized when we worship a person, and all things become beautiful and everything falls in place when we worship God. There is a difference between night and day if you can see it, perceive it, but to a blind and ignorant person, everything is same.