Here are the games that are good for low spec gaming
1.
Doom (1993), although Doom was release back in the early days of 1990's, it still had a great fanbase, and heck there's a source port named,
ZDoom, There's also a forums like
Doomworld, there's allot of mods for this game.
2.
Undertale (2015), since this game is based on retro rpg games, with a twist of both buttet hell, and C64 graphics.
3.
Half-Life 2 (2004), don't let the game fool you since it looks this game needs a high spec pc, but this game can run in any windows pc's (XP & Up), and this don't need any fancy stuff to run.
4. Minecraft (2009), we all know what Minecraft is.
5.
Roblox (2006), we also know what Roblox is too.