Answer

If you mean the highest among the four deva classes, it is the Vaimānika devas; and within that group, the Anuttara devas are described as the highest species of gods. ( jainpedia.org)

If you mean the rarest and most spiritually valuable birth overall, Jain Dharma teaches that human birth is the most precious, because liberation (moksha) is possible only in human form. ( jainpedia.org)

Explanation

The four classes of devas in Jain cosmology are Bhavanavāsin, Vyantara, Jyotiṣka, and Vaimānika. The Vaimānikas dwell in the upper world and are the most elevated among these classes. ( jainpedia.org)

But Jain teaching gives the greatest importance to human birth, because even though heavenly birth brings great pleasure, it still remains within saṃsāra, the cycle of rebirth. Human life is the special opportunity for spiritual effort and liberation. ( jainpedia.org)

Spiritual Understanding

So, from a worldly point of view, Vaimānika devas are the highest among the four devas. But from a liberation point of view, human birth is more valuable than deva birth in Jain Dharma. ( jainpedia.org)

Takeaway

Highest deva class: Vaimānika. Rarest and most important birth for moksha: Human birth. ( jainpedia.org)