  Molecular dynamic simulations for systems with $D=2,3$ Lennard-Jones-like
interactions are studied. In the model, we assume that, at long distances, the
two-body attractive potential decays as $r^{-\alpha}$. Thermodynamic
extensivity (nonextensivity) is observed for $\alpha > D$ ($0\leq \alpha \leq
D$). Particular attention is payed to the liquid-gas critical point located, in
the temperature-pressure plane, at ($T_c,P_c$). ($T_c,P_c$) are, in the $N\to
\infty$ limit ($N\equiv$ number of molecules), {\em finite} for $\alpha > D$
and {\em diverge} for $\alpha \leq D$ (as $(\alpha - D)^{-1}$ for $\alpha/D \to
1 + 0$). However, the variables $T_c^* \equiv T_c/N^*$ and $P_c^* \equiv
P_c/N^*$ with $N^* \equiv [N^{1-\alpha/D} -1]/[1-\alpha/D]$ remain {\em finite
for all} $\alpha$. Thus, the extensive and nonextensive regions become unified,
as recently conjectured. These results should be useful for discussing
gravitation and some special fluids
