Is a God, let's say Ganesh, more powerful than an avatar? Yes I know they are part of God but still?
As you say, whether a deity such as Ganesha or an avatar like Krishna, both are part of God and both therefore have the power of God. Two things, however, to consider: one is the purity and power of your love and attunement (personal connection) with God in the form you are attracted to, and two, that it is the role of the God-realized avatar to be a savior of souls.
I know of several stories from India in which the devotee was having visions of Krishna or Kali but who, in time, was gifted the grace of a God-realized guru. In each story, the deity informed the devotee that he needed a guru, and with the devotee’s agreement a guru was sent in human form. These stories illustrate the importance of a guru.
Few people in this world are so blessed and so God-devoted to attract such a guru. For many, it is in the lineage of a satguru where the guru’s touch is received by the transmission of true disciples. Either way that contact seems to be necessary.
And why might that be? Because it is the plan of salvation and the plan of creation that souls within creation (in the God-designed and blessed human form, especially) can and do achieve Self-realization within and through the creation and not merely by supernatural means. If we are “made in the image of God” we shouldn’t have to die “to get to heaven” nor should God have to redeem us by a special act or miracle involving suprasensory beings. We are meant to find God within ourselves and we just need a little help to ignite the spark that inflames the heart with devotion so that grace can be transmitted directly.
Blessings to you, friend!