NOTE: I'm not asking about Brahman which is attribute less. I'm asking about Saguna Brahman or Ishwara according to the orthodox Advaita Vedanta of Shri Adi Shankaracharya.
Here this blog says
Answer: This is a commentary of Adi Shankara on the Bhagavat Gita verse 11.43, what people do not understand is that Bhagavat Gita is actually elaborating the Upanishad, so the Samskrutam words in 11.43 “न त्वत्समोऽस्त्यभ्यधिकः ” meaning : There is none equal to you or greater than you .
This has been put due to being inspired by the Shvetahshvatara Upanishad, following is the verse from the Shvethashvatara Upanishad
न तस्य कार्यं करणं च विद्यते न तत्समश्चाभ्यधिकश्च दृश्यते।
परास्य शक्तिर्विविधैव श्रूयते स्वाभाविकी ज्ञानबलक्रिया
Translation: Oh him there is no body, nor instruments of action, there is none equal or greater to be seen, his supreme power creates this manifold world which is of the nature of knowledge, power and execution.
Shvetahshvatara Upanishad Chapter 6 verse 8
In fact Adi Shankara quotes this in his Brahma Sutra Bhashya to prove that Ishwara is without any form. Please find the link below which explains this in detail.
So if according to Adviata Ishwara is formless and can assume any form which the devotee desires, are some forms more holier than others, like what is the difference between the forms of Lord Vishnu or Lord Shiva and say a Greek God Zeus or some tribal God or a celebrity film star. Why can't someone worship the form of God Zeus or Lord Indra or some random celebrity as Ishwara? Like is there a preference for Upasya Roopa according to orthodox Advaita?
If all forms of Ishwara is equally valid, then, how are, holy Hindu forms of Lord Vishnu and Lord Shiva, more special and holy than other forms of Greek and Roman gods or popular celebrities?