All Emulator links listed in this section are Microsoft Windows based emulators and have been tested with Windows 10 64bit, if you have an older or newer OS they may or may not work, some have 32bit and 64bit versions so make sure you download the correct version for your operating system, while 32bit works fine on a 64bit system, 64bit programs don't work on 32bit systems.
Some of the emulator links also contain other OS releases, ie.. Apple Mac, BeOS, Linux, Wii etc... I've not tested any of these as I don't have access to any of these systems.
There are many other emulators available for the various systems but these are the only ones I've tested and the Gradius related games play fine on these.
If more than one emulator is listed for each system then the top listed one is the one to test first.
https://www.mamedev.org/ - MAME 0.244 - 25/05/2022 - Windows Console Version Tested.
https://www.advancemame.it/ - - AdvanceMAME v3.9 - 08/09/2018 - Graphical front end for MAME.
Local Hosting - Sparcade v2.33b - 22/12/1999 - DOS Only Emulator by Dave Spicer - Will only run in DOS and maybe DOSBOX
https://raine.1emulation.com/ - Raine 0.93.5a - 24/06/2022 - MAME alternative
https://mamedev.org/ - MAME 0.244 - 25/05/2022 - Windows Console Version Tested.
https://yabause.org/ - Yabause 0.9.15 - 24/08/2016 - 32bit or 64bit.
No Link - pSX emulator v1.13 - Simple and best PlayStation emulator - 27/08/2007
https://www.epsxe.com/ - ePSXe 2.0.5 - 24/06/2016
https://www.pcsx2.net/ - PCSX2 1.6.0 - 07/05/2020
http://virtuanes.s1.xrea.com:8080/ - VirtuaNES 0.97 (Japanese) - 14/10/2007
http://www.snes9x.com - Snes9x-1.53-win32 - 25/04/2011
http://www.dolphin-emulator.com - Dolphin 4.0 - 2013 - (Updated often).
http://www.magicengine.com - Magic Engine 1.1.3 - 26/05/2008
https://mijet.eludevisibility.org/XM6%20Pro-68k/XM6%20Pro-68k.html - XM6 - Best X68000 Emulator - 30/05/2022
https://web.archive.org/web/20041028050133/http://www.geocities.co.jp/SiliconValley-Sunnyvale/1779/ - WinX68kHighSpeed v0.95 (English Version) - 06/03/2004
Try it on your Windows PC first, if not try DOSBox
https://www.dosbox.com/ - Windows 95, 98, 98SE, ME, 2000, XP, Vista, 7, 8, 8.1, 10 - v 0.74-3DOSBox
https://mgba.io/ - mGBA - v0.10.1 - 10/01/2023
https://mgba.io/ - mGBA - v0.10.1 - 10/01/2023
NO LINK - KEmulator Lite Version Ver 0.9.8 - 05/12/2008 - No longer available on the main site.
http://nlmsx.generation-msx.nl/ - NLMSX 0.48 - 12/06/2003 - Old but runs fast with no problems.
https://vice-emu.sourceforge.io/ - VICE 3.6.1 - 24/01/2022
http://www.winape.net/ - WinAPE32 2.0 Beta 2 - 06/01/2016
Local Hosting - zx32 version 2.00.04.04 (beta) - 04/04/2000 (hosted here as the original site no longer exists).
http://www.retropc.net/yui/xmil.html - X Millennium Ver 0.26d (Japanese) - 14/11/2000
http://retropc.net/pi/ - XM8 1.70 (Japanese) - 23/01/2018 - eXellent Multi-platform emulator type 8 - 'XM8' based on ePC-8801MA
https://www.yui.ne.jp/np2/ - Neko Project II Ver 0.86 (Japanese) - 06/03/2016