Blessed, or (R' Schwab) we join together with:
You - which establishes our relationship to God as an I-Thou, relating to the Other as a person, implying a certain intimacy, relatability, etc. But:
O God, the Tetragrammaton, the unreachable transcendent God. How does that relate to Atah? There is a dialectic tension set up here, only partially synthesized by:
Our God, the aspect of God through which we relate, perhaps the immanent God, as the Kabbalists would say, the Ohr Pnimi, the Internal Light, the Divinity that permeates reality. The two, the Transcendent and Immanent God, are of course One, and our relation to Him is through this dialectic tension.
And God of our Fathers. We don't only relate to Him directly, but because of, and in part mediated by, the experiences of our ancestors, particularly the Three Fathers (and fore mothers? not specified, except in certain heterodox rituals, but surely implied).
God of Abraham, God of Isaac, and God of Jacob. Why repeat Elohei for each? The commentators suggest it's that each acknowledged God as individuals, not just as an inheritance from their father. I would go further, noting that each Father had a different experience of God, yet they all related to the One God.
Avraham discovered God, through an "intellective" process, and inspired by that, spread God's word and goodness to all around him, eventually converting 318 of his soldiers/retainers.
Yitzchak experienced God through being the sacrificial victim, saved at the last minute by that God - so he experienced the fear of God innately, both physical fear of death in a Godly act, and the spiritual "yirah me'ahavah", the fear of God knowing that on Him hangs one's life, and one then loves God who sustains and saves his life (viz. R. Levi Yitzchak of Berdichev on Vayosha').
Yaakov was the wanderer. Perhaps his essence was to be a "simple man, a dweller in tents", but he was forced by circumstance to wander, spending 22 years with Lavan, and decades more in Egypt at the end of his life, praying to God at each cusp of his life to help him deal with all difficulties. Yaakov's God is perhaps closest to most of us, as we are in exile, and need the aid of the Deus Absconditus, not knowing if we deserve it or even can get it at all.