Set the monitor you want games to run on as your primary monitor. Right click on your desktop, select "display settings", and click on the monitor you want games to run on. If you can't tell which monitor is which, click on "identify". Under the "multiple displays" heading, click on "make this my main display" for that monitor. Then go to the heading "scale & layout" down a bit below that, and set the "display resolution" to be the correct value for each monitor. Windows should say "(Recommended)" after the correct resolution.

You can also try exiting the Steam client. Then start it up again. Move the Steam client to the monitor you want the games to open on. Then launch your game. If you launch games from an app on your secondary monitor, I guess it could confuse Steam about what monitor you intend to use.

There are some shortcuts that may help, too. Windows key + p will let you control how Windows configures your screens. You can temporarily disable the secondary display before launching a game, then reenable it and extend your desktop. Or Windows key + shift + arrow key will send programs to another display.

Steam's Big Picture Mode was designed for running games on HDTVs I think, but it should work alright for launching games on dual monitors. I've never personally used it, but I've heard some people talk about it. If I ever wanted to start games on a different monitor, what I did was temporarily set that monitor as my primary monitor. BPM sounds like it might work for that, though.

Alright first thank you for writing a response, I already have tried what you suggested in the first paragraph, I do always open steam on my main monitor so I dont think thats to much of an issue, I will try to use the method of disabling my second monitor before starting these games. Its only really messing with 3 games but mainly gang beast and buckshot roulette so im trying to uninstall and reinstall because the main issue is the resolution it loads up in and it wont change back no matter what I do.

I will also try big picture mode.

Thank you very much sir.

Well just redownloaded buckshot as its a small games so it was done by the time i finished writing this it did seem to open back up regularly

Did you ever find a fix for this? Im having the same issue with a couple games and it's driving me crazy. I have tried everything I can think of, and so far, the only solution I have is to launch the game, then disable my second monitor and then re-enable it. However, it still sometimes doesn't fix the issue, and I have to leave my second monitor disabled to play.