Shalom and thank you for your question! You ask what is so good about resurrection of the dead. After a hundred and twenty (the amount of years that Moses lived, and because he lived the fullest life spiritually, we wish ourselves the same amount of years,) we go upstairs and live it up with the angels, basking in the Divine Presence, what could be better?
The Rambam, (Maimonides,) agrees with you. He feels that Gan Eden is the zenith of life for the Jewish soul, indeed, to bask in the Divine Presence. The Ramban, (Nachmanides,) feels that Gan Eden is an intermediary stage between life in the material world, and life in the time of the Redemption, when souls will be resurrected into bodies.
Before we go into who is right, let’s look at a concept taught in the book of Tanya, a basic text of Chassidic teaching. There it explains in depth the anatomy of a Jewish soul. This is something that takes a library to explain, but briefly for our purpose, the soul has five levels, Nefesh, Ruach, Neshama, Chaya and Yechida. This is listed from the lowest level to the highest. The soul in this material world gives life to our physical bodies. The first three levels on the list are in progressively deeper and more subconscious layers of our awareness. We are only aware on a conscious level of our Nefesh. To complicate matters, we actually have two Nefashot. A G-dly soul – the Nefesh that lets us know that we want to be on the side of good, and have values and meaning in our lives, and an animal soul. The animal soul lets us know that we want to take care of our needs and wants. As such, it plays an important role, but as you may guess, it tends to also get in the way of the aims of the G-dly soul. The two souls actually live in a state of battle, at one point in time the G-dly soul wins, and we go join a minyan for prayer, attend a Torah class, call our great aunt, or walk the kid across the road. At another point we may put the alarm on snooze and miss the minyan, (not talking about illness etc.) or snap at our spouse, child, etc. Hello animal soul! That’s the tale of two souls, the story of our exile. In the world to come, the world of Redemption, we will have worked so hard on our spiritual awareness, that we will have won over the animal soul to be totally on the same side as the G-dly soul, so that our body will rise of its own accord to praise the L-rd, it will no longer be an effort or a conflict. (This will be achieved with help from Heaven in addition to our own efforts.)
Thus, the Chassidic approach concurs with the approach of the Ramban, the peak of the soul’s achievement is Resurrection, when the material world will only help and not hinder the revelation and expression of G-dliness.
The supernal worlds of the afterlife, before the final Redemption, are places where G-dliness is revealed, and they are full of light and spiritual ecstasy. But surprisingly enough, the light there is not revealed in its entire glory.
The physical world does such a good job of covering up the G-dly light that sustains it, that that light needs to be a higher ‘voltage’ than even the light of Gan Eden! When we toil to learn Torah and keep the mitzvot, despite the obstacles in the physical world, we are refining it and bringing it to the point where it no longer covers up the G-dly light. Then that ‘high-voltage’ light will be revealed in all its glory, and the material world and animal soul will support G-dliness rather than conflict with it.
That’s why it is so important to keep in mind the goal of the final Redemption, which includes the Resurrection.
