EMU7800 is described as 'An Atari 7800 emulator implemented using Microsoft's .NET platform. Most ProSystem (7800) and VCS (2600) titles run well. EMU7800 runs on Windows Vista SP2 and higher systems. Performance is sufficient on current hardware' and is an app in the Gaming Software category. There are three alternatives to EMU7800 for Windows, AmigaOS, Linux, Mac and MorphOS. The best alternative is Mame, which is both free and Open Source. Other great apps like EMU7800 are BizHawk (Free, Open Source) and ProSystem (Free, Open Source).
MAME stands for Multiple Arcade Machine Emulator. When used in conjunction with images of the original arcade game's ROM and disk data, MAME attempts to reproduce that game as faithfully as possible on a more modern general-purpose computer.
BizHawk is a multi-system emulator designed predominantly around the production of Tool Assisted Speedruns (TAS). BizHawk focuses on core accuracy and power user tools while still being an easy-to-use emulator for casual gaming.