I haven't used Parallels, but it used to come for free with a new Mac. This website is a source of unprecedented access to all kinds of pc,mac or linux software.
I don't use VMware (I like the free stuff), but I've heard good things about it. Emulators Sony Playstation Mac OS X PCSX. This one is somewhat confusing to download I think you have to compile the emulator by hand. As with anything Apple-related, it should be pretty straightforward. I haven't actually installed it on a Mac, I've used a friend's computer, so I can't help you with installation. I would recommend Boot Camp for 3D stuff. Boot Camp (Free) - Comes with all Intel Macs It allows multiple operating systems to run on your computer. Virtualbox is not quite as lightweight as Q. The ROM contains the video game files of ESPN Baseball Tonight (29611) and the emulator acts as the game console. It supports emulating x86, x86-64bit, PPC PowerMac, PPC PREP, SPARC32, MIPS, and ARM processors. There are emulators for different platforms like Windows, Android, iOS and Mac OS X. There are versions for Windows, Mac OS X, Mac OS 9 (PowerPC), Linux (x86), Pocket PC. Mini vMac is an emulator for the Macintosh Plus and Macintosh SE. This is the Mac emulator currently used by the Internet Archive for their MacOS System 7.1 Compilation. Oddly enough, it runs on PPC Macs, in addition to Intel Macs. The C source code is released under the GNU General Public License. Q is a great lightweight CPU emulator for OS X. Professionally supported enhancement of Wine Q (Free) Wine (and Crossover) do not require an actual copy of Windows installed on your machine. I would recommend Winebottler, a free binary installer that also allows you to turn a Windows executable into a simple application that launches in X11. You do need to install the Developer Tools, included on your computer's install disc. I would also not recommend compiling it yourself. ports for Linux, DOS, Windows, and unofficial ports for Xbox and macOS. I don't know how well it works with 3D stuff. ZSNES is a free software Super Nintendo Entertainment System emulator written mostly in x86.
I highly recommend Wine, which allows for running Windows applications without actually emulating the whole Windows OS. When using the term "emulator", it is important to distinguish between something that acts like Windows to applications (like Wine/Crossover) and something that acts like a PC to Windows (most of the other solutions) so that Windows can be installed.