  In quasi-2D quantum magnets the ratio of N\'eel temperature $T_\text N$ to
Curie-Weiss temperature $\Theta_\text{CW}$ is frequently used as an empirical
criterion to judge the strength of frustration. In this work we investigate how
these quantities are related in the canonical quasi-2D frustrated square or
triangular $J_1$-$J_2$ model. Using the self-consistent Tyablikov approach for
calculating $T_\text N$ we show their dependence on the frustration control
parameter $J_2/J_1$ in the whole N\'eel and columnar antiferromagnetic phase
region. We also discuss approximate analytical results. In addition the field
dependence of $T_\text N(H)$ and the associated possible reentrance behavior of
the ordered moment due to quantum fluctuations is investigated. These results
are directly applicable to a class of quasi-2D oxovanadate antiferromagnets. We
give clear criteria to judge under which conditions the empirical frustration
ratio $f=\Theta_\text{CW}/T_\text N$ may be used as measure of frustration
strength in the quasi-2D quantum magnets.
