  Gapless Dirac fermions appear as quasiparticle excitations in various
condensed-matter systems. They feature quantum critical points with critical
behavior in the 2+1 dimensional Gross-Neveu universality class. The precise
determination of their critical exponents defines a prime benchmark for
complementary theoretical approaches, such as lattice simulations, the
renormalization group and the conformal bootstrap. Despite promising recent
developments in each of these methods, however, no satisfactory consensus on
the fermionic critical exponents has been achieved, so far. Here, we perform a
comprehensive analysis of the Ising Gross-Neveu universality classes based on
the recently achieved four-loop perturbative calculations. We combine the
perturbative series in $4-\epsilon$ spacetime dimensions with the one for the
purely fermionic Gross-Neveu model in $2+\epsilon$ dimensions by employing
polynomial interpolation as well as two-sided Pad\'e approximants. Further, we
provide predictions for the critical exponents exploring various resummation
techniques following the strategies developed for the three-dimensional scalar
$O(n)$ universality classes. We give an exhaustive appraisal of the current
situation of Gross-Neveu universality by comparison to other methods. For large
enough number of spinor components $N\geq 8$ as well as for the case of
emergent supersymmetry $N=1$, we find our renormalization group estimates to be
in excellent agreement with the conformal bootstrap, building a strong case for
the validity of these values. For intermediate $N$ as well as in comparison
with recent Monte Carlo results, deviations are found and critically discussed.
