How to initialize content of a RAM without using Megawizard

Quartus II simply ignores TEXTIO during synthesis, though it should really be giving you an error that you're doing something unsupported! File I/O should be supported for initializing constants. It's only a hard error if you want to describe a process that loads the contents of a file "at runtime". Off and on, I see designs where someone is attempting to do exactly that, e.g. load a JPEG into device RAM and manipulate it. FPGA != general purpose processor attached to your computer :)