Summary: Real and complex Monge-Ampère equations \[ (A)\;\text{det}\Biggl({\partial^2 u\over \partial x_i \partial x_j}\Biggr)= f(|x|, u, |\nabla u|),\;x\in \mathbb{R}^N,\;(B)\;\text{det}\Biggl({\partial^2 u\over \partial z_i \partial\overline z_j}\Biggr)= f(|z|, u, |\nabla u|),\;z\in \mathbb{C}^N \] are considered in the entire spaces \(\mathbb{R}^N\) and \(\mathbb{C}^N\), respectively, \(N\geq 2\). A unified fixed-point approach is used to generate various conditions for (A) to have radial, strictly convex solutions \(u(x)\) in \(\mathbb{R}^N\) that are asymptotic to positive constant multiples of \(|x|\) as \(|x|\to \infty\), and for (B) to have radial, strictly plurisubharmonic solutions \(u(z)\) in \(\mathbb{C}^N\) that are asymptotic to positive constant multiples of \(\log|z|\) as \(|z|\to \infty\).